Methods and devices for the production of hydrocarbons from carbon and hydrogen sources

ABSTRACT

Devices and methods are described for converting a carbon source and a hydrogen source into hydrocarbons, such as alcohols, for alternative energy sources. The influents may comprise carbon dioxide gas and hydrogen gas or water, obtainable from the atmosphere for through methods described herein, such as plasma generation or electrolysis. One method to produce hydrocarbons comprises the use of an electrolytic device, comprising an anode, a cathode and an electrolyte. Another method comprises the use of ultrasonic energy to drive the reaction. The devices and methods and related devices and methods are useful, for example, to provide a fossil fuel alternative energy source, store renewable energy, sequester carbon dioxide from the atmosphere, counteract global warming, and store carbon dioxide in a liquid fuel.

CLAIM OF PRIORITY

This application is a division of U.S. application Ser. No. 13/597,196,filed Aug. 28, 2012, which is continuation of U.S. application Ser. No.12/151,206, filed May 5, 2008, which claims benefit of U.S. ProvisionalPatent Application No. 60/927,641, filed May 4, 2007, U.S. ProvisionalPatent Application No. 61/001,944, filed on Nov. 6, 2007 and U.S.Provisional Patent Application No. 61/007,491, filed on Dec. 13, 2007,all of which are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention generally relates to devices and methods for theproduction of hydrocarbons from carbon and hydrogen sources, such as,the production of alcohols from gaseous, carbonaceous influents in thepresence of water. Additionally, the invention relates to the productionof hydrocarbons using hydrogen gas influents. The invention relates toproduction of hydrocarbons using electrolytic, plasma or ultrasonicenergy. The invention also generally relates to devices and methods forcarbon dioxide sequestration; the generation of carbon influents; thegeneration of hydrogen influents; stopping, slowing or reversing globalwarming; storing carbon dioxide as a liquid hydrocarbon based fuel;storing renewable energy; providing long-term, stable energy prices; andrenewably producing hydrogen gas and hydrogen ions.

BACKGROUND OF THE INVENTION

Mankind is dependent upon energy. Over the past 100 years mankind hasadopted fossil fuels as its primary source of energy, but has neglectedthe long term environmental health of the Earth by failing to recognizeand address the environmental impact resulting from the extended use offossil fuels.

There is almost unanimous scientific agreement that the Earth's climateis directly affected by human activity, especially the combustion offossil fuels to obtain energy. The combustion of fossil fuels comprisesthe oxidation of carbon-based molecules by oxygen, thus producing carbondioxide. Carbon dioxide is recognized as a global warming gas. Levels ofcarbon dioxide gas in Earth's atmosphere today are nearly 30 percenthigher than they were prior to the start of the Industrial Revolutionand mankind's dependence on fossil fuels, based on records extendingback 650,000 years.

The increase in atmospheric carbon dioxide levels is overwhelminglyrecognized in the scientific community as driving global climate change.Recent climate changes include, for example, rapidly increasing averageworldwide temperatures and accelerating polar ice cap destruction.Records indicate that 11 of the last 12 years were among the 12 warmeston record worldwide. According to NASA, the polar ice cap is now meltingat the rate of 9 percent per decade and arctic ice thickness hasdecreased 40 percent since the 1960's.

The detrimental effects on mankind of global warming and increasingenergy prices have spurred mankind's interest in alternative, andparticularly renewable, sources of energy. Renewable energy flowsinvolve natural, perpetual phenomena such as sunlight, wind, tides, andgeothermal heat. For example, the use of wind, water, and solar energyare widespread in some countries and the mass production of electricityusing renewable energy sources has become more commonplace in recenttimes.

The present invention will make use of carbon dioxide as an influent,and in some methods sequester carbon dioxide from the atmosphere. Thepresent invention also provides devices and methods for the cleanproduction of hydrocarbons with a goal toward using those hydrocarbonsas alternatives to fossil fuel consumption. The description herein ofproblems and disadvantages of known apparatus, methods, and devices isnot intended to limit the invention to the exclusion of these knownentities. Indeed, embodiments of the invention may include one or moreof the known apparatus, methods, and devices without suffering from thedisadvantages and problems noted herein.

SUMMARY OF THE INVENTION

One embodiment of the invention is a device and method for theproduction of hydrocarbons using a carbon source and water as thehydrogen source in an electrolytic reaction. Another embodiment of theinvention is a device and method for the production of hydrocarbonsusing a carbon source and water as the hydrogen source in an plasmaassisted electrolytic reaction. Another embodiment of the invention is adevice and method for the production of hydrocarbons using a carbonsource and water as the hydrogen source in an sonochemical assistedelectrolytic reaction. A further embodiment of the invention is a deviceand method for the production of hydrocarbons using gaseous hydrogen asa feed.

There is a need for new energy sources that will not further exacerbatemankind's already detrimental effect upon the environment, particularlyin the context of global warming. There is a further need for devicesand methods for providing energy in a form that is capable ofimmediately replacing existing fossil fuels used in internal combustionpower sources such as automobile engines. Additionally needed aredevices and processes to store renewable energy in energy-dense, readilyaccessible formats. There also is a need for devices and processes toremove CO₂ from the atmosphere and to store it in a liquid or solid(i.e. plastic) form in order to reduce the effect on the environment ofhuman-induced global warming.

Moreover, there is a need for new devices and processes that affordgreater control, selectivity, efficiency, and yield coupled with reducedcomplexity and capital costs than current devices and processes for theindustrial-scale production of lower hydrocarbons from gaseous,carbonaceous influents. There is a need for new devices and processesthat provide economically viable renewable energy alternatives.

Accordingly, there is provided herein an electro-hydrocarbon device forthe electrolytic production of hydrocarbons from gaseous, carbonaceousinfluents. The electro-hydrocarbon device comprises a first input foraccepting a gaseous influent comprising at least one of carbon monoxidegas and carbon dioxide gas; a second input for accepting an influentselected from the group consisting of water-containing influents andhydrogen-containing influents; an electrical power source; a cathodeconnected to the electrical power source and exposed to the first input;an anode connected to the electrical power source and exposed to thesecond input; and an electrolyte connecting the anode and cathode.Electrical power from the electrical power source causes reduction ofthe gases at the cathode to form hydrocarbons.

There also is provided a process for the electrolytic production ofhydrocarbons from gaseous, carbonaceous influents. The process comprisescontacting a gaseous influent comprising at least one of carbon monoxidegas and carbon dioxide gas with a cathode; contacting an influentselected from the group consisting of water-containing influents andhydrogen-containing influents with an anode connected to the cathode byan electrolyte; and applying an electrical potential between the cathodeand the anode. The electrical potential applied between the cathode andthe anode causes reduction of the gases at the cathode to formhydrocarbons.

There further is provided another device for the electrolytic productionof hydrocarbons from gaseous, carbonaceous influents. The devicecomprises a first input for accepting a gaseous influent, the gaseousinfluent comprising carbon dioxide gas; a second input for accepting aninfluent selected from the group consisting of water-containinginfluents and hydrogen-containing influents; a deoxygenation deviceconnected to the first input and that is capable of reducing at leastsome of the carbon dioxide gas in the gaseous influent to produce carbonmonoxide gas; and an electro-hydrocarbon device connected to thedeoxygenation device and the second input and that is capable ofreducing at least some of the carbon monoxide gas and any remainingcarbon dioxide gas to produce hydrocarbons.

Moreover, there is provided another process for the electrolyticproduction of hydrocarbons from gaseous, carbonaceous influents. Theprocess comprises treating a gaseous influent comprising carbon dioxidegas with a deoxygenation device that is capable of reducing at leastsome of the carbon dioxide gas in the gaseous influent to produce carbonmonoxide gas; and treating the carbon monoxide gas and any remainingcarbon dioxide gas with an electro-hydrocarbon device that is capable ofreducing at least some of the carbon monoxide gas and any remainingcarbon dioxide gas to produce hydrocarbons.

Additionally provided is a process for sequestering carbon dioxide fromthe atmosphere, storing carbon dioxide in a liquid fuel, and slowing,stopping or reversing global warming. The process comprises collectingcarbon dioxide gas from the atmosphere; treating the carbon dioxide gaswith a deoxygenation device that is capable of reducing at least some ofthe carbon dioxide gas in the gaseous influent to produce carbonmonoxide gas; and treating the carbon monoxide gas and any remainingcarbon dioxide gas with an electro-hydrocarbon device that is capable ofreducing at least some of the carbon monoxide gas and any remainingcarbon dioxide gas to produce hydrocarbons.

A process for storing renewable energy also is provided. The processcomprises producing electrical energy from a renewable energy source andtreating a gaseous influent comprising at least one of carbon monoxidegas and carbon dioxide gas with an electro-hydrocarbon device that iscapable of reducing at least some of the gaseous influent to producehydrocarbons. The electro-hydrocarbon device utilizes the electricenergy produced from the renewable energy source.

These and other devices, processes, variations, features, and advantageswill be apparent from the description provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature and scope of the invention will be elaborated in the detaileddescription which follows, in connection with the figures.

FIG. 1 is a graph illustrating the free energy versus enthalpy for thechemical reduction of carbon monoxide to methanol.

FIG. 2 is a graph illustrating the free energy versus enthalpy for thechemical reduction of carbon dioxide to methanol.

FIG. 3 illustrates an exemplary electro-hydrocarbon device and processdescribed herein.

FIG. 4 illustrates an exemplary electro-hydrocarbon device and processdescribed herein.

FIG. 5 illustrates an exemplary deoxygenation device and processdescribed herein.

FIG. 6 illustrates an exemplary combineddeoxygenation/electro-hydrocarbon device and process described herein.

FIG. 7 illustrates an exemplary combineddeoxygenation/electro-hydrocarbon device and process described herein.

FIG. 8 is a graph illustrating the free energy versus enthalpy for thechemical reduction of carbon dioxide to carbon monoxide.

FIG. 9 illustrates an exemplary process and device for carbon dioxideextraction described herein.

FIG. 10 illustrates an exemplary process and device for the electrolysisof water.

FIG. 11 illustrates an exemplary process and device for theelectro-hydrocarbon synthesis using hydrogen as a reactant.

FIG. 12 illustrates an exemplary process and device using plasma energyto ionize carbon dioxide or hydrogen.

FIG. 13 illustrates an exemplary process and device for producinghydrocarbons using ultrasonic energy.

FIG. 14 illustrates an exemplary process and device for creatinghydrogen gas using ultrasonic energy.

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this disclosure, the singular forms “a,” “an,” and“the” include plural reference unless the context clearly dictatesotherwise.

All technical and scientific terms used herein have the same meanings ascommonly understood by one of ordinary skill in the art to which thisinvention belongs, excepting terms, phrases, and other language definedherein. All publications mentioned herein are cited for the purpose ofdescribing and disclosing the embodiments. Nothing herein is to beconstrued as an admission that the embodiments described are notentitled to antedate such disclosures by virtue of prior invention.

Before the present devices and processes are described, it is to beunderstood that this invention is not limited to the particular devices,processes, methodologies or protocols described, as these may vary. Itis also to be understood that the terminology used in the description isfor the purpose of describing the particular versions or embodimentsonly, and is not intended to limit the scope of the present inventionwhich will be limited only by the appended claims. For simplicity, eachreference referred to herein shall be deemed expressly incorporated byreference in its entirety as if fully set forth herein.

One embodiment of the invention is a device and method for theproduction of hydrocarbons using a carbon source and a hydrogen sourcein an electrolytic reaction. A second embodiment of the invention is adevice and method for the production of hydrocarbons using a carbonsource and a hydrogen in an plasma reaction. A third embodiment of theinvention is a device and method for the production of hydrocarbonsusing a carbon source, and hydrogen source in an ultrasonic reaction.All reactions may be powered from energy harnessed from a renewableresource, such as solar and/or wind.

The Fischer-Tropsch process is a way to produce hydrocarbons (liquid)from gas in the presence of a catalyst at high temperature and pressure.See e.g., H. H. Storch, N. Golumbic and R. B. Anderson, TheFischer-Tropsch and related syntheses, John Wiley & Sons, New York(1951). The present devices and methods seek to run reactions at muchlower temperature and pressure than the The Fischer-Tropsch, such asless than about 5 atmosphere and less than about 200° C. The presentdevices and methods seek to kinetically drive the reactions with energyderived from renewable sources, such as wind and solar. The renewableenergy is supplied to the reactions described herein as electricalenergy, ultrasonic energy, plasma energy, and combinations thereof.

I. Device and Method for the Production of Hydrocarbons Using anElectrolytic Reaction.

The first method and device involves producing hydrocarbons, andpreferably hydrocarbons, from a carbon source and a hydrogen source inan electrolytic reaction.

Electro-Hydrocarbon Devices

The electro-hydrocarbon devices may comprise, for example, a first inputfor accepting a gaseous influent comprising a carbon source, such as atleast one of carbon monoxide gas and carbon dioxide gas; a second inputfor accepting a hydrogen source, such as an influent selected from thegroup consisting of water-containing influents and hydrogen-containinginfluents; an electrical power source; a cathode connected to theelectrical power source and exposed to the first input; an anodeconnected to the electrical power source and exposed to the secondinput; and an electrolyte connecting the anode and cathode. In theelectro-hydrocarbon device, electrical power from the electrical powersource causes reduction of the gases at the cathode to formhydrocarbons.

The device may be used to accomplish a process comprising contacting agaseous influent comprising at least one of carbon monoxide gas andcarbon dioxide gas with a cathode; contacting an influent selected fromthe group consisting of water-containing influents andhydrogen-containing influents with an anode connected to the cathode byan electrolyte; and applying an electrical potential between the cathodeand the anode. The electrical potential applied between the cathode andthe anode causes reduction of the gases at the cathode to formhydrocarbons.

Accordingly, the electro-hydrocarbon device may function by drivinghydrogen ions from the anode through the electrolyte to the cathode,where the hydrogen ions participate in the reduction of carbon monoxideand/or carbon dioxide to form hydrocarbons.

The gaseous influent that is contacted with the cathode of theelectro-hydrocarbon devices may be from any applicable supply of carbonmonoxide gas and/or carbon dioxide gas including, for example, theatmosphere, industrial combustion processes, syngas, and so forth.Preferably, the influent may be pre-treated in order to removeundesirable contaminants and/or inerts that might detrimentally affectthe functioning of the electro-hydrocarbon devices. For example,contaminants and inerts that might poison the cathode or adsorb onto thecathode, thus affecting the cathode's ability to catalyze the reductionof carbon monoxide gas and/or carbon dioxide gas to hydrocarbons,preferably may be removed before the influent is contacted with thecathode of the electro-hydrocarbon devices. Such contaminants and inertspotentially include, but are not limited to, heavy metals such as lead,iron, copper, zinc, and mercury; sulfur-containing species such ashydrogen sulfide and mercaptans; arsenic; amines; carbon monoxide (CO)in some instances; nitrogen (N₂); nitrogen oxides (NO_(x)); ammonia(NH₃); sulfur dioxide (SO₂); hydrogen sulfide (H₂S); organicheterocyclic compounds containing nitrogen or sulfur; and so forth.

In a preferred embodiment, the gaseous influent to the cathode of theelectro-hydrocarbon device consists essentially of carbon monoxide gas.In another preferred embodiment, the gaseous influent to the cathode ofthe electro-hydrocarbon device consists essentially of carbon dioxidegas. In a further preferred embodiment, the gaseous influent to thecathode of the electro-hydrocarbon device consists essentially of carbonmonoxide and carbon dioxide gas.

The influent that is contacted with the anode of the electro-hydrocarbondevices may be a hydrogen-containing influent because hydrogen, orhydrogen ions, is a direct reactant in the reduction of carbon monoxideand carbon dioxide to hydrocarbons. Alternatively, the influent that iscontacted with the anode of the electro-hydrocarbon devices may be awater-containing influent. In the case of a water-containing influent,the water is hydrolyzed at the anode to release hydrogen ions thattravel through the electrolyte to the cathode to participate in thereduction of carbon monoxide and carbon dioxide to hydrocarbons. Oxygengas is a by-product of this reaction and is vented off of the anode andreleased to the atmosphere from the electro-hydrocarbon device.

Without desiring to be limited thereto, it is believed that thefollowing exemplary overall reactions for the reduction of carbonmonoxide and carbon dioxide to hydrocarbons occur at the cathode andanode of the electro-hydrocarbon device.

For the conversion of carbon monoxide into alcohols:

nCO+(2n)H₂

C_(n)H_((2n+1))OH+(n−1)H₂O  (1.1)

For the conversion of carbon dioxide into alcohols:

nCO₂+(3n)H₂

C_(n)H_((2n+1))OH+(2n−1)H₂O  (1.2)

Accordingly, exemplary half-reactions for the production of methanol andethanol from carbon monoxide and carbon dioxide can be written asfollows.

For the conversion of carbon monoxide to methanol, the followinghalf-reactions are believed to take place:

Cathode: CO+4H⁺+4e ⁻

CH₃OH  (2.1)

Anode: 2H₂

4H⁺+4e ⁻  (2.2)

Overall: CO+2H₂

CH₃OH  (2.3)

For the conversion of carbon monoxide to ethanol, the followinghalf-reactions are believed to take place:

Cathode: 2CO+8H⁺+8e ⁻

CH₃CH₂OH+H₂O  (3.1)

Anode: 4H₂

8H⁺+8e ⁻  (3.2)

Overall: 2CO+4H₂

CH₃CH₂OH+H₂O  (3.3)

For the conversion of carbon dioxide to methanol, the followinghalf-reactions are believed to take place:

Cathode: CO₂+6H⁺+6e ⁻

CH₃OH+H₂O  (4.1)

Anode: 3H₂

6H⁺+6e ⁻  (4.2)

Overall: CO₂+3H₂

CH₃OH+H₂O  (4.3)

For the conversion of carbon dioxide to ethanol, the followinghalf-reactions are believed to take place:

Cathode: 2CO₂+12H⁺+12e ⁻

CH₃CH₂OH+3H₂O  (5.1)

Anode: 6H₂

12H⁺+12e ⁻  (5.2)

Overall: 2CO₂+6H₂

CH₃CH₂OH+3H₂O  (5.3)

The hydrogen that is consumed in the exemplary half-reactions listedabove, as explained, may be produced by electrolysis of water,preferably using renewable energy, where the influent to the secondinput is a water-containing influent. Accordingly, taking into accountthis associated reaction, the overall reactions for theelectro-hydrocarbon device as a whole could be written as follows in thecase of a water-containing influent.

For the conversion of carbon monoxide into alcohols:

nCO+(n+1)H₂O

C_(n)H_((2n+1))OH+nO₂  (6.1)

For the conversation of carbon dioxide into alcohols:

nCO₂+(n+1)H₂O

C_(n)H_((2n+1))OH+(3n/2)O₂  (6.2)

Accordingly, taking into account this associated reaction, exemplaryhalf-reactions for the production of methanol and ethanol from carbonmonoxide and carbon dioxide could be written as follows.

For the conversion of carbon monoxide to methanol, the followinghalf-reactions are believed to take place:

Cathode: CO+4H⁺+4e ⁻

CH₃OH  (7.1)

Anode: 2H₂O

4H⁺+4e ⁻+O₂  (7.2)

Overall: CO+2H₂O

CH₃OH+O₂  (7.3)

For the conversion of carbon monoxide to ethanol, the followinghalf-reactions are believed to take place:

Cathode: 2CO+8H⁺+8e ⁻

CH₃CH₂OH+H₂O  (8.1)

Anode: 4H₂O

8H⁺+8e ⁻+2O₂  (8.2)

Overall: 2CO+3H₂O

CH₃CH₂OH+2O₂  (8.3)

For the conversion of carbon dioxide to methanol, the followinghalf-reactions are believed to take place:

Cathode: CO₂+6H⁺+6e ⁻

CH₃OH+H₂O  (9.1)

Anode: 3H₂O

6H⁺+6e ⁻+3/2O₂  (9.2)

Overall: CO₂+2H₂O

CH₃OH+3/2O₂  (9.3)

For the conversion of carbon dioxide to ethanol, the followinghalf-reactions are believed to take place:

Cathode: 2CO₂+12H⁺+12e ⁻

CH₃CH₂OH+3H₂O  (10.1)

Anode: 6H₂O

12H⁺+12e ⁻+3O₂  (10.2)

Overall: 2CO₂+3H₂O

CH₃CH₂OH+3O₂  (10.3)

The electro-hydrocarbon devices described herein facilitate thereactions described above and therefore are useful for the production ofhydrocarbons, and in particular C₁ alcohols, and preferably methanol,ethanol, propanol, butanol, pentanol, heptanol, and other loweralcohols, from gaseous influents comprising at least one of carbonmonoxide and carbon dioxide. These alcohols provide, among otherbenefits, an energy-dense and relatively clean burning combustiblesource of thermal energy. Additionally, the electro-hydrocarbon devicesprovide methods of applying electrical energy to force the reactionsshown above.

The methods and devices described herein are not limited to theproduction of alcohols, and include the production of any suitablehydrocarbon, such as alcohols, alkanes, alkenes, alkynes, aromatichydrocarbons, ethers, aldehydes, ketones, carboxylic acids, esters,amines, and any organic, carbon-containing molecule having a carboncontent of about 12 carbon atoms or less containing one or more of thefollowing groups: alcohol, alkane, alkene, alkyne, ether, aldehyde,ketone, carboxylic acid, ester, and amine.

The hydrocarbons produced by the reactions described herein may be usedas further reactants. For example, the hydrocarbons may be used as afeedstock for the production of plastics. For example, the hydrocarbonsmay be used as a reactant in the further production of highercarbon-content hydrocarbons. The further production using the producedhydrocarbon may be by a process described herein or by a traditionalhydrocarbon synthesis process. It is possible to further react theproduced hydrocarbon to form synthetic petrochemicals. These includepetroleum ether, certain solvents, gasoline, kerosene, fuel for heatingand diesel fuel, lubricating oils, petroleum jelly, paraffin wax, andpitch, or tar.

The hydrocarbons produced by the reactions described herein may be usedas fuels or stored in a fuel container. It is possible to use thehydrocarbons produced by the reactions described in an internal orexternal combustion engine. The hydrocarbons produced by the reactionsdescribed herein may be oxidized, burned, or combusted in an engine orfuel cell installed in any suitable vehicle, such as an automobile,aircraft, or military vehicle. It is possible to oxidize the producedhydrocarbon in a traditional combustion engine. Additionally, thedevices/reactors described herein may also be installed into any suchcombustion engine, such that the hydrocarbons produced by the reactormay be oxidized to power the engine.

For example, a vehicle, such as a car may have solar panels installed onits roof. These solar panels collect sunlight and convert the solarenergy into electricity. The electricity generated may then be used topower the electrolytic reaction described in this Section I or any ofthe other reactions described in Sections II and III.

The alcohols methanol and ethanol are preferred products of theelectro-hydrocarbon device and its associated operating process. Forexample, it may be preferable that the gaseous influent to the cathodeof the electro-hydrocarbon device consist essentially of carbon monoxidegas and the alcoholic effluent from the cathode to comprise methanol. Italso may be preferred that the gaseous influent to the cathode of theelectro-hydrocarbon device consist essentially of carbon monoxide gasand the alcoholic effluent from the cathode to comprise ethanol.Alternatively, it may be preferable that the gaseous influent to thecathode of the electro-hydrocarbon device consist essentially of carbondioxide gas and the alcoholic effluent from the cathode to comprisemethanol. In another alternative, it also may be preferred that thegaseous influent to the cathode of the electro-hydrocarbon deviceconsist essentially of carbon dioxide gas and the alcoholic effluentfrom the cathode to comprise ethanol.

The electro-hydrocarbon device preferably operates at a temperature inthe range from less than about 50° C. to less than about 900° C.Preferably, the electro-hydrocarbon device operates at a temperatureless than about 400° C. More preferably, the electro-hydrocarbon deviceoperates at a temperature less than about 200° C. A lower operatingtemperature of the electro-hydrocarbon device is desirable because ofreduced energy costs to operate the device and because, as explained inmore detail later, lower temperatures thermodynamically favor thereduction of carbon monoxide and carbon dioxide to alcohols.

The electro-hydrocarbon device preferably operates at a pressure in therange from less than about 1 atm to about 50 atm. Preferably, theelectro-hydrocarbon device operates at a pressure less than about 10atm. More preferably, the electro-hydrocarbon device operates at apressure less than about 5 atm. Even more preferably, theelectro-hydrocarbon device operates at a pressure less than about 1 atm.A lower operating pressure of the electro-hydrocarbon device may bedesirable because of reduced energy costs to operate the device.However, a higher operating pressure may be desirable because, asindicated in Equations 1.1 and 1.2 above and in accordance with LeChatelier's principle, the equilibrium systems will respond to anincrease in pressure by shifting towards the products of the reaction.Accordingly, the benefit of lower energy costs may be weighed againstthe disadvantages of operating the electro-hydrocarbon devices at lowerpressures, such as lower equilibrium conversion of the reactants toalcohols and potentially reduced reaction rates.

Modern industrial processes for the synthesis of alcohols, primarilymethanol, from CO and/or CO₂ and H₂ (i.e., “syngas”) generally fall intotwo categories: high-pressure syntheses, where reactors are operated atabout 100 atm to about 600 atm in pressure and at about 250° C. to about400° C. and ZnO/Cr₂O₃ catalysts typically are employed; and low-pressuresyntheses, where reactors are operated at about 20 atm to about 100 atmin pressure and at about 230° C. to about 300° C. and CuO/ZnO catalystswhich generally contain chromium promoters (e.g., Cr₂O₃) or aluminumpromoters (e.g., Al₂O₃) typically are employed. Traditional syngassyntheses do not use electrical current or potential to drive thereduction of carbon monoxide and carbon dioxide to alcohols.

The electro-hydrocarbon devices described herein advantageously may becapable of functioning at lower temperatures and pressures thantraditional CO/CO₂ alcohol syntheses. For example, theelectro-hydrocarbon devices may function at temperatures of less thanabout 900° C., more preferably at less than about 400° C., even morepreferably at less than about 200° C., and most preferably at less thanabout 50° C. while maintaining reaction rates approximating, equivalentto, or even superior to the reaction rates of traditional syngas-alcoholsyntheses. The electro-hydrocarbon device may function at pressures ofless than about 50 atm, more preferably less than about 10 atm, evenmore preferably less than about 5 atm, and most preferably less thanabout 1 atm, again while maintaining reaction rates approximating,equivalent to, or even superior to the reaction rates of traditionalsyngas-alcohol syntheses. Accordingly, the electro-hydrocarbon devicesdescribed herein potentially represent a significant energy savingsvis-à-vis the traditional syngas-alcohol syntheses.

Because lower reaction temperatures thermodynamically favor theproduction of alcohols from carbon monoxide and carbon dioxidereactants, the electro-hydrocarbon devices may produce a higherequilibrium conversion of reactants to alcohols than is accomplishedusing traditional, higher temperature syngas-alcohol syntheses.

FIGS. 1 and 2 illustrate the free energy vs. enthalpy of, respectively,the production of methanol from carbon monoxide (Equation 2.3: CO+2H₂

CH₃OH) and the production of methanol from carbon dioxide (Equation 4.3:CO₂+3H₂

CH₃OH+H₂O). In FIG. 1 for the production of methanol from carbonmonoxide, it is apparent that the free energy (ΔG) of the reactionincreases with increasing reaction temperature. Likewise in FIG. 2 forthe production of methanol from carbon dioxide, it is apparent that thefree energy of the reaction increases with increasing reactiontemperature. It is believed that similar relationships between reactiontemperature and free energy are to be found for the production of otheralcohols (e.g., proponal, butanol, pentanol, and heptanol) from carbonmonoxide and carbon dioxide.

A lower free energy thermodynamically favors the production of theproducts of an equilibrium reaction. Accordingly, it is advantageousfrom a thermodynamic perspective for the production of alcohols by thereduction of carbon monoxide or carbon dioxide to proceed at a lowertemperature, thus favoring a higher equilibrium production of alcohols.The single-pass yield of the electro-hydrocarbon devices (e.g., thepercent conversion of the cathodic influent without a recycle stream) islimited to the theoretical maximum equilibrium conversion at thereaction temperature, as dictated by the free energy.

Of course, lower reaction temperatures also typically have a negativeimpact on reaction rate. Accordingly, the desirability of an increasedconversion of reactants to products (i.e. increased production ofalcohols at equilibrium) must be weighed against the speed with whichthis conversion is desired to take place. Nevertheless, because thereduction of carbon monoxide and carbon dioxide to form alcohols isdriven by electric current or potential in the electro-hydrocarbondevices, it is believed that an acceptable rate of reaction may beachieved even at low temperatures that thermodynamically favor highconversion of the carbon monoxide and carbon dioxide reactants toalcohol products.

The electro-hydrocarbon devices therefore facilitate the production ofalcohols from carbon monoxide and carbon dioxide because theelectro-hydrocarbon devices are capable of functioning at lowertemperatures than traditional syngas-alcohol syntheses, and thusachieving higher equilibrium conversion of the reactants to alcohols,while still maintaining a relatively high reaction rate.

An additional advantage of the electro-hydrocarbon devices is that thedevices may be simpler, smaller, readily scaleable, and can even be madeto be portable. Because traditional syngas-alcohol syntheses take placeat relatively high temperatures and pressures, the chemical processequipment used to perform industrial scale syngas-alcohol syntheses iscomplex, large, not easily scaleable, and not portable. Currentindustrial scale syngas-alcohol equipment is expensive to produce andcomplex to design and implement. The electro-hydrocarbon devicesdescribed herein, in comparison, may be less expensive to produce andmore simple to design, implement, and maintain because, for example,they involve less components and operate at less strenuous conditions.Additionally, the electro-hydrocarbon devices are less dangerous tooperate than industrial syngas-alcohol equipment because of the lowerpressures and temperatures at which the electro-hydrocarbon devices arecapable of operating.

The cathode of the electro-hydrocarbon devices may comprise variouselectrocatalysts (or “alcohol catalysts”). Electrocatalysts include, ingeneral, applicable metal catalysts, metal-supported catalysts,metal-oxide supported catalysts, and superconducting materials.

In regards to electrocatalysts for the production of methanol, thefollowing exemplary list of catalysts may be used as electro-catalyticcathodes in the electro-hydrocarbon devices described herein:

various metal-supported catalysts, for example using the metals copper(Cu), silver (Ag), nickel (Ni), ruthenium (Ru), rhenium (Rh), andpalladium (Pd), and supports such as zinc oxide (ZnO), zirconia (ZrO₂),aluminum oxide (Al₂O₃), titanium dioxide (TiO₂), silica (SiO₂), andceria (CeO₂);

ZnO/Cr₂O₃ catalysts;

Cu-based catalysts (CuB), optionally doped with chromium (Cr), zirconium(Zr), or thorium (Th);

Cu/ZnO and CuO/ZnO catalysts, preferably aluminum (Al₂O₃), chromium(Cr₂O₃), cesium (CeO₂), or zirconium (ZrO₂) promoted, such asCu/ZnO/Al₂O₃ and Cu/ZnO/ZrO₂, and optionally doped with metals such asAl, Sc, Cr, Mg, Mn, Rh, Rn, Ti, and Zr, and ions thereof;

Cu—Mo_(0.3)Zr_(0.7)O₂ (M=Ce, Mn, and Pr) catalysts;

Cu catalysts supported on ultrapure silica or γ-alumina supports andwith Ca, Zn, and La oxide promoters (e.g., Ca/Cu/SiO₂, Zn/Cu/SiO₂, andLa/Cu/SiO₂);

Cu/ZnO/ZrO₂/Al₂O₃/Ga₂O₃;

alloys of copper with hafnium, zirconium and in particular thorium;

various intermetallic alloys such as catalysts derived nickel from rareearth metals like lanthanum;

binary thorium-copper alloys;

intermetallic lanthanide-copper alloys (CeCu_(x), where x=1.3 to 3.2)such as CeCu₂, preferably with Ti, Zr, or Al for improved resistance tocarbon dioxide poisoning;

zirconia-supported catalysts such as Cu/ZrO₂, Au/ZrO₂, and Pd/ZrO₂,preferably made from chloride or sulfate starting salts such as copperchloride and zirconium sulfate and optionally silver promoted;

Cu(100) and Ni/Cu(100);

the superconductor YBa₂Cu₃O₇; and

ceria-supported palladium (Pd—CeO₂).

In regards to electrocatalysts for the production of ethanol, thefollowing exemplary list of catalysts may be used as electro-catalyticcathodes in the electro-hydrocarbon devices described herein:

alkali-doped ZnO—Cr₂O₃, Zr—Zn—Mn—Pd, Cu—ZnO, and Cu—ZnO—Al₂O₃;

modified Fischer-Tropsch catalysts such as alkali-doped CuO—CoO—Al₂O₃,CuO—CoO—ZnO—Al₂O₃, and alkali-promoted NiO—TiO₂ catalysts;

alkali-doped sulfides such as MoS₂;

promoted Rh—SiO₂ catalysts such as those promoted with Li salts(Rh—Li—SiO₂);

composite catalysts of copper-rare earth oxide catalysts (e.g.,Cu—La₂Zr₂O₇) mixed with an HY zeolite;

K—MoO₃-γAl₂O₃ catalysts with varied loading of Mo to select for ethanolor other desired oxygenate products;

rhodium catalysts promoted by reducible metal-oxides such as Fe₂O₃, MnOor TiO₂;

Rh₁₀Se—TiO₂ catalysts;

Rm-Sm—V/SiO₂ catalysts;

tetragonal ZrO₂ and Pd modified ZrO₂ catalysts;

Rh/Al₂O₃ catalysts promoted with manganese (Mn); and

silica supported cobalt (10 w/o) or iron (5 w/o) catalysts.

In regards to catalysts for the production of C₃₊ alcohols and otheroxygenates, the following exemplary list of catalysts may be used aselectro-catalytic cathodes in the electro-hydrocarbon devices describedherein:

cesium (Cs) promoted Cu—ZnO methanol catalysts and potassium (K)promoted Cu_(0.5)Mg₅CeO_(x) catalysts, preferably for the production ofisobutanol, and optionally combined in a dual catalyst configurationwith a methanol catalyst (e.g., Cs—Cu—ZnO—Cr₂O₃ and Cs—ZnO—Cr₂O₃) inorder to produce methyl isobutyl ether (MIBE), methyl tertiary butylether (MTBE), and dimethyl ether (DME) in various ratios via directcoupling of methanol and isobutanol;

monoclinic ZrO₂ and Pd modified ZrO₂ catalysts, preferably for theproduction of isobutanol;

CuO—ZnO—ZrO₂—Fe₂O₃—MoO₃—ThO₂—Cs₂O catalysts, preferably for theproduction of C₃₊ alcohols hydrocarbons; and

cobalt catalysts supported on silica aerogel, preferably for theproduction of C₉-C₁₅ hydrocarbons.

The following publications describing catalysts that may be useful aselectro-catalytic cathodes in the electro-hydrocarbon devices areincorporated herein by reference in their entirety:

-   X-M. Liu, G. Q. Lu, Z-F. Yan and J. Beltramini, Recent advances in    catalysts for methanol synthesis via hydrogenation of CO and CO ₂,    Industrial Engineering Chemical Research, vol. 42, p. 6518-6530    (2003);-   J. Skrzpek, M. Lachowska, M. Grzesik, J. Sloczynski and P. Nowak,    Thermodynamics and kinetics of low pressure methanol synthesis, The    Chemical Engineering Journal, vol. 58, p. 101-108 (1995);-   E. Blasiak, Polish Patent PRL 34000 (1947);-   H-B. Chen, D-W. Liao, L-J. Yu, Y-J. Lin, J. Yi, H-B. Zhang and K-R.    Tsai, Influence of trivalent metal ions on the surface structure of    a copper-based catalyst for methanol synthesis, Applied Surface    Science, vol. 147, p. 85-93 (1999);-   G. C. Chinchen, P. J. Denny, D. G. Parker, M. S. Spencer and D. A.    Whan, Mechanism of methanol synthesis from CO ₂ /CO/H ₂ mixtures    over copper/zinc oxide/alumina catalysts: use of 14C-labelled    reactants, Applied Catalyst, vol. 30, p. 333-338 (1987);-   E. G. Baglin, G. B. Atkinson and L. J. Nicks, Methanol synthesis    catalysts from thorium-copper intermetallics. Preparation and    evaluation, Industrial Engineering Chemical Production Research    Development, vol. 20, p. 87-90 (1981);-   J. R. Jennings, R. M. Lambert, R. M. Nix, G. Owen and D. G. Parker,    Novel methanol synthesis catalysts derived from intermetallic    precursors: CO ₂ poisoning and molecular mechanism of the synthesis    reaction, Applied Catalysis, vol. 50, p. 157-170 (1989);-   J. Weigel, R. A. Koeppel, A. Baiker and A. Wokaun, Surface species    in CO and CO ₂ hydrogenation over copper/zirconia: On the methanol    synthesis mechanism, Langmuir, vol. 12, p. 5319-5329 (1996);-   A. Baiker and D. Gasser, Journal of Faraday Transactions, vol.    85(4), p. 999 (1989);-   J. S. Lee, K. I. Moon, S. H. Lee, S. Y. Lee and Y. G. Kim, Modified    Cu/ZnO/Al ₂ O ₃ catalysts for methanol synthesis from CO ₂ /H ₂ and    CO/H ₂, Catalysis Letters, vol. 34, p. 93-99 (1995);-   Y. Nitta, T. Fujimatsu, Y. Okamoto and T. Imanaka, Effect of    starting salt on catalytic behaviour of Cu—ZrO ₂ catalysts in    methanol synthesis from carbon dioxide, Catalysis Letters, vol.    17, p. 157-165 (1993);-   J. F. Deng, Q. Sun, Y. L. Zhang, S. Y. Chen and D. A. Wu, A novel    process for preparation of a Cu/ZnO/Al ₂ O ₃ ultrafine catalyst for    methanol synthesis from CO ₂ +H ₂ : comparison of various    preparation methods, Applied Catalysis: A, vol. 139, p. 75-85    (1996);-   J. Weigel, C. Frohlich, A. Baiker and A. Wokaun, Vibrational    spectroscopic study of IB metal/zirconia catalysts for the synthesis    of methanol, Applied Catalysis A: General, vol. 140, p. 29-45    (1996);-   A. Gotti and R. Prins, Basic metal oxides as cocatalysts for Cu/SiO    ₂ catalysts in the conversion of synthesis gas to methanol, Journal    of Catalysis, vol. 178, p. 511-519 (1998);-   J. Nerlov and I. Chokendorff, Methanol synthesis from CO ₂ , CO and    H ₂ over Cu(100) and Ni/Cu(100), Journal of Catalysis, vol. 181, p.    271-279 (1999);-   J. B. Hansen, in Handbook of Heterogenous Catalysis, ed. G. Ertl, H.    Knozinger and J. Weitkamp, VCH, Weinheim, p. 1856 (1997);-   J. Wambach, A. Baiker and A. Wokaun, CO ₂ hydrogenation over    metal/zirconia catalysts, Physical Chemistry-Chemical Physics, vol.    1, p. 5071-5080 (1999);-   L. Z. Gao and C. T. Au, CO ₂ hydrogenation to methanol on a YBa ₂ Cu    ₃ O ₇ catalyst, Journal of Catalysis, vol. 189, p. 1-15 (2000);-   Y. Matsumura, W-J. Shen, Y. Ichihashi and M. Okumura,    Low-temperature methanol synthesis catalyzed over ultrafine    palladium particles supported on cerium oxide, Journal of Catalysis,    vol. 197, p. 267-272 (2001);-   B. J. Liaw and Y. Z. Chen, Liquid-phase synthesis of methanol from    CO ₂ /H ₂ over ultrafine CuB catalyst, Applied Catalysis: A, vol.    206, p. 245 (2001);-   H-B. Chen, D-W. Liao, L-J. Yu, Y-J. Lin, J. Yi, H-B. Zhang and K-R.    Tsai, Influence of trivalent metal ions on the surface structure of    a copper-based catalyst for methanol synthesis, Applied Surface    Science, vol. 147, p. 85-93 (1999);-   J. Slozynski, R. Grabowski, A. Kozlowska, P. Olszewski, M.    Lachowska, J. Skrzypek and J. Stoch, Effect of Mg and Mn oxide    additions on structural and adsorptive properties of Cu/ZnO/ZrO ₂    catalysts for the methanol synthesis from CO ₂, Applied Catalysis A:    General, vol. 249, p. 129-138 (2003);-   K. A. Pokrovski and A. T. Bell, Effect of the dopants on the    activity of Cu—Mo _(0.3) Zr _(0.7) O ₂ (M=Ce, Mn and Pr) for CO    hydrogenation to methanol, Journal of Catalysis, vol. 244, p. 43-51    (2006);-   H. H. Storch, N. Golumbic and R. B. Anderson, The Fischer-Tropsch    and related syntheses, John Wiley & Sons, New York (1951);-   G. Natta, U. Colombo and I. Pasquon, in Catalysis, ed. P. H. Emmett,    vol. V, Chapter 3, Reinhold Publishing Co., New York (1957);-   P. Di Raffaele, A. Paggini and V. Lagana, French Patent 2,482,583;-   W. Keim and W. Falter, Catalysis Letters, vol. 3, p. 59 (1989);-   K. Smith and R. B. Anderson, Journal of Canadian Chemical    Engineering, vol. 61, p. 40 (1983);-   K. J. Smith and R. B. J. Anderson, Journal of Catalysis, vol. 85, p.    428 (1984);-   J. G. Nunan, C. E. Bogdan, R. G. Herman and K. Klier, Catalysis    Letters, vol. 2, p. 49 (1989);-   P. Courty, D. Durand, E. Freund and A. Sugier, Journal of Molecular    Catalysis, vol. 17, p. 241 (1982);-   S. Uchiyama, Y. Ohbayashi, T. Hayasaka and N. Kawata, Applied    Catalysis, vol. 42, p. 143 (1988);-   W. P. Dianis, Applied Catalysis, vol. 30, p. 99 (1987);-   H. Kusama, K. Okabe, K. Sayama and H. Arakawa, CO ₂ hydrogenation to    ethanol over promoted Rh-SiO ₂ catalysts, Catalysis Today, vol.    28, p. 261-266 (1996);-   R. Kieffer, M. Fujiwara, L. Udron and Y. Souma, Hydrogenation of CO    and CO ₂ toward methanol, alcohols and hydrocarbons on promoted    copper-rare earth oxides catalysts, Catalysis Today, vol. 36, p.    15-24 (1997);-   K. Klier, A. Beretta, Q. Sun, O. C. Feeley and R. G. Herman,    Catalytic synthesis of methanol, higher alcohols and ethers,    Catalysis Today, vol. 36, p. 3-14 (1997);-   G-Z. Bian, L. Fan, Y-L. Fu and K. Fujimoto, High temperature    calcined K—MoO ₃-γAl ₂ O ₃ catalysts for mixed alcohols synthesis    from syngas: Effects of Mo loadings, Applied Catalysis A: General,    vol. 170, p. 255-268 (1998);-   H. Kurkata, Y. Izumi and K. Aika, Chemistry Communications, p.    389-390 (1996);-   A-M. Hilmen, M. Xu, M. J. L. Gines and E. Iglesia, Synthesis of    higher alcohols on copper catalysts supported on alkali-promoted    basic oxides, Applied Catalysis A: General, p. 355-372 (1998);-   M. Lachowska, Synthesis of higher alcohols. Enhancement by the    addition of methanol or ethanol to the syngas, Reaction Kinetic    Catalysis Letters, vol. 67(1), p. 149-154 (1999);-   H. Y. Luo, W. Zhang, H. W. Zhou, S. Y. Huang, P. Z. Lin, Y. J. Ding    and L. W. Lin, A study of Rh—Sm—V/SiO ₂ catalysts for the    preparation of C ₂-oxygenates from syngas, Applied Catalysis A:    General, vol. 214, p. 161-166 (2001);-   D. He, Y. Ding, H. Luo and C. Li, Effects of zirconia phase on the    synthesis of higher alcohols over zirconia and modified zirconia,    Journal of Molecular Catalysis A: Chemical, vol. 208, p. 267-271    (2004);-   M. Ojeda, M. L. Granados, S. Rojas, P. Terreros, F. J. Garcia    and J. L. G. Fierro, Manganese-promoted Rh/Al ₂ O ₃ for C    ₂-oxygenates synthesis from syngas. Effect of managanese loading,    Applied Catalysis A: General, vol. 261, p. 47-55 (2004);-   B. C. Dunn, P. Cole, D. Covington, M. C. Webster, R. J. Pugmire    and G. P. Huffman, Silica aerogel supported catalysts for    Fischer-tropsch synthesis, Applied Catalysis A: General, vol.    278, p. 233-238 (2005);-   Y. A. Ryndin, R. F. D. Hicks, A. T. Bell and Y. I. Yermakov, Effects    of metal-support interactions on the synthesis of methanol over    palladium, J. Catal., vol. 70, p. 287 (1981);-   W. E. Wallace, Proceedings of Int. Symp. Hydrides for Energy    Storage, Pergamon Press, ed. A. F. Andresen and A. J. Maeland    (1977);-   G. B. Atkinson and L. J. Nicks, Mischmetal-nickel alloys as    methanation catalysts, J. Catal., vol. 46, p. 417 (1977);-   E. G. Baglin, G. B. Atkinson and L. J. Nicks, U.S. Pat. No.    4,181,630 (1980);-   E. G. Baglin, G. B. Atkinson and L. J. Nicks, Methanol synthesis    catalysts from thorium-copper intermetallics. Preparation and    Evaluation, Ind. Eng. Chem. Prod. Res. Dev., vol. 20, p. 87-90    (1981);-   S. J. Bryan, J. R. Jennings, S. J. Kipling, G. Owen, R. M. Lambert    and R. M. Nix, Appl. Catal., vol. 40, p. 173 (1988);-   K. Klier, V. Chatikanvangi, R. G. Herman and G. W. Simonds,    Catalytic synthesis of methanol from CO/H ₂ : IV. The effects of    carbon dioxide, J. Catal., vol. 74, p. 343 (1982);-   C. Liu, D. Willcox, M. Garland and H. H. Kung, J., The rate of    methanol production on a copper-zinc oxide catalyst: The dependence    on the feed composition, Catal., vol. 90, p. 139 (1984);-   G. G. Chinchen, P. J. Denny, D. G. Parker, M. S. Spencer and D. A.    Whan, Appl. Catal., vol. 30, p. 333, (1987);-   M. Muhler, E. Tornqvist, L. P. Nielsen and B. S. Clausen, On the    role of adsorbed atomic oxygen and CO ₂ in copper based methanol    synthesis catalysts, Catal. Lett., vol. 25, p. 1 (1994);-   J. Weigel, R. A. Koeppel, A. Baiker and A. Wokaun, Surface species    in CO and CO ₂ hydrogenation over copper/zirconia: on the methanol    synthesis mechanism, Langmuir, vol. 12, p. 5319-5329 (1996);-   D. Mignard, M. Sahibzada, J. Duthie and H. W. Whittington, Methanol    synthesis from flue-gas CO ₂ and renewable electricity: a    feasibility study. Int. J. Hydrogen Energy, vol. 28, p. 455-464    (2003);-   V. A. Pena-O'Shea, N. N. Menendez, J. D. Tornero and J. L. G. Fiero.    Unusually high selectivity to C ₂₊ alcohols on bimetallic CoFe    catalysts during CO hydrogenation, Catal. Lett., vol. 88, p. 123-128    (2003);-   X. M. Ma, G. D. Lin and H. B. Zhang, Co-decorated carbon    nanotube-supported Co—Mo—K sulphide catalyst for higher alcohol    synthesis, Catal. Lett., vol. 111, p. 141-151 (2006);-   M. M. Bhasin, W. T. Bartley, P. C. Ellgen and T. P. Wilson, J.    Catal., vol. 54, p. 120 (1985);-   M. Ichikawa, T. Fukushima and K. Shikakura, Proc. 8^(th) ICC    (Berlin), 11-69 (1984);-   M. Xu and E. Iglesia, Initial carbon-carbon bond formation during    synthesis gas conversion to higher alcohols on K—Cu—Mg ₅ CeO _(x)    catalysts, Catal. Lett., vol. 51, p. 47-52 (1998);-   M. Saito, M. Takeuchi, T. Fujitani, J. Toyir, S. Luo, J. Wu, K.    Ushikoshi, K. Mori and T. Watanabe, Advances in the research between    NIRE and RITE for developing a novel technology for methanol    synthesis from CO ₂ and H ₂, ICCDU V Karlruhe (1999);-   M. Sahibzada, I. S. Metcalfe and D. Chadwick, Methanol synthesis    from CO/CO ₂ —H ₂ over Cu/ZnO/Al ₂ O ₃ at differential and finite    conversions, Journal of Catalysis, vol. 174(2), p. 111-118 (1998);    and-   Y. Matsumura, W-J. Shen, Y. Ichihashi and M. Okumura,    Low-temperature methanol synthesis catalyzed over ultrafine    palladium particles supported on cerium oxide, Journal of Catalysis,    vol. 197, p. 267-272 (2001).

Other catalysts also may be selected for use as electrocatalysts in theelectro-hydrocarbon devices in accordance with the description herein.

The electrolyte of the electro-hydrocarbon devices may comprise variousionic conductors. Preferably, the electrolyte is selected from the groupof protonic conductors. For example, protonic conductors comprisingpolymeric materials and solid acids may be preferred for low temperature(e.g., about 80° C. to about 300° C.) operation of theelectro-hydrocarbon device. Protonic conductors comprising ceramic mixedoxides such as cerates and zirconates may be preferred for hightemperature (e.g., about 500° C. to about 900° C.) operation of theelectro-hydrocarbon device. Preferably, the protonic conductor will havean ionic conductivity (a) between about 0.01 S/cm to about 0.1 S/cm.

In regards to polymeric materials and solid acids, the followingexemplary list of protonic conductors may be used as electrolytes in theelectro-hydrocarbon devices described herein:

polyetheretherketone (PEEK) membranes;

solid acids consisting of CsHSO₄, preferably for operation of the deviceat temperatures from about 150° C. to about 160° C.;

silicon oxide nafion composite membranes, preferably for operation ofthe device at about 80° C. to about 140° C.;

polybenzimidazole (PBI) electrolyte membranes, preferably for operationof the device at temperatures from about 120° C. to about 200° C.;

poly(aryl ether sulfone) copolymers containing 2,5-biphenylpyridine andtetramethyl biphenyl, preferably for operation of the device attemperatures from about 130° C. to about 400° C.;

nafion/titanium dioxide composite membranes, preferably for operation ofthe device at temperatures from about 80° C. to about 120° C. and atrelative humidity from about 26% to about 100%;

poly-2,5-benzimidazole (ABPBI), preferably for operation of the deviceat temperatures up to about 200° C.;

amorphous cesium thio-hydroxogermanate, preferably for operation of thedevice at temperatures from about 100° C. to about 275° C. and at lowrelative humidity;

NH₄PO₃—(NH₄)₂SiP₄O₁₃ composites, preferably for operation of the deviceat temperatures up to about 250° C.;

nanohybrid membranes of zirconia/polytetramethylene oxide, preferablyfor operation of the device at temperatures from about 150° C. to about300° C.;

nanoporous proton-conducting membranes based on polytetrafluroethylene(PTFE), preferably for operation of the device at temperatures of about130° C.; and

nanoporous proton-conducting membranes consisting of ceramic powder,polymer binder (polytetrafluoroethylene, PTFE) and aqueous acid,preferably for operation of the device at temperatures up to about 300°C.

In regards to ceramic mixed oxides, the following exemplary list ofprotonic conductors may be used as electrolytes in theelectro-hydrocarbon devices described herein:

perovskites of the form ABO₃ such as BaZrO₃, SrZrO₃, BaCeO₃, and SrCeO₃doped with rare earth oxides, preferably for operation of the device attemperatures above about 600° C.;

mixed perovskites of the type A₂B′B″O₆(AB′_(1/2)B″_(1/2)O₃) where A isBa⁺² and B′ and B″, respectively, are trivalent ions (Er, Gd, La, Yb,and Ca) and pentavalent ions (Nb, Ta, and Te);

zirconate perovskites consisting of SrZr_(0.90)Y_(0.10)O_(3-α) attemperatures from about 550° C. to about 750° C.;

BaCe_(0.9)Y_(0.1)O_(3-α), preferably for operation of the device inatmospheres containing at least about 9% CO₂;

Ce-doped Ba₂In₂O₅ prepared from nanopowders, preferably for operation ofthe device at temperatures from about 100° C. to about 300° C.;

other proton conducting acceptor-doped perovskite alkaline earthcerates, zirconates, niobates, and titanates such asSr(Ce_(0.9)Y_(0.1))O_(3-α), Ba₂YSnO_(5.5), Ba(Zr_(0.9)Y_(0.1))O_(3-α),Ba₃Ca_(1.17)Nb_(1.83)O_(9-α), Sr(Zr_(0.9)Y_(0.1))O_(3-α),Ba(Ti_(0.95)SC_(0.05))O_(3-α), and Sr(Ti_(0.95)Sc_(0.05))O_(3-α); and

other Ba—Zr, Sr-CE, and Ba—Ce mixed oxides.

The following publications describing protonic conductors that may beuseful as electrolytes in the electro-hydrocarbon devices areincorporated herein by reference in their entirety:

-   S. M. Halle, D. A. Boysen, C. R. I. Chisholm and R. B. Merle, Solid    acids as fuel cell electrolytes, Nature, vol. 410, p. 910-913    (2001);-   K. T. Adjemian, S. J. Lee, S. Srinivasan, J. Benziger and A. B.    Bocarsly, Silicon oxide Nafion composite membranes for    proton-exchange membrane fuel cell operation at 80-140° C., Journal    of the Electrochemical Society, vol. 149(3), p. A256-A261 (2002);-   Y. L. Ma, J. S. Wainright, M. H. Litt and R. F. Savinell,    Conductivity of PBI membranes for high-temperature polymer    electrolyte fuel cells, Journal of the Electrochemical Society, vol.    151(1), p. A8-A16 (2004);-   E. K. Pefkianakis, V. Deimede, M. K. Daletou, N. Gourdoupi and J. K.    Kallitis, Novel polymer electrolyte membrane, based on pyridine    containing poly (ether sulfone), for application in high-temperature    fuel cells, Macomolecular Rapid Communications, vol. 26, p.    1724-1728 (2005);-   E. Chalkova, M. B. Pague, M. V. Fedkin, D. J. Wesolowski and S. N.    Lvov, Nafion/TiO ₂ proton conductive composite membranes for PEMFCs    operating at elevated temperature and reduced relative humidity,    Journal of the Electrochemical Society, vol. 152(6), p. A1035-A1040    (2005);-   J. A. Asensio and P. Gomez-Romero, Recent developments on proton    conducting poly2,5-benzimidazole (APBI) membranes for high    temperature polymer electrolyte membrane fuel cells, Fuel Cells,    vol. 5(3), p. 336-343 (2005);-   S. A. Poling, C. R. Nelson and S. W. Martin, New intermediate    temperature proton conductors: hydrated heavy alkali    thio-hydroxogermanates, Materials Letters, vol. 60, p. 23-27 (2006);-   X. Chen, Z. Huang and C. Xia, Fabrication and characterization of    solid state proton conductor (NH ₄)₂ SiP ₄ O ₁₃ —NH ₄ PO ₃ for fuel    cells operated at 150-250° C., Solid State Ionics, vol. 177, p.    2413-2416 (2006);-   J-D. Kim and I. Honma, High-temperature-tolerant, proton-conducting    polytetramethylene oxide/zirconia hybrid membranes, Journal of the    Electrochemical Society, vol. 151(9), p. A1396-A1401 (2004);-   S. Reichman, T. Duvdevani, A. Aharon, M. Philosoph, D. Golodnitsky    and E. Peled, A novel PTFE-based proton-conductive membrane, Journal    of Power Sources, vol. 153, p. 228-233 (2006);-   S. Reichman, A. Ulus and E. Peled, PTFE-based solid polymer    electrolyte membrane for high-temperature fuel cell applications,    Journal of the Electrochemical Society, vol. 154(3), p. B327-333    (2007);-   M. J. Scholten, J. Schoonman, J. C. van Miltenburg and H. A. J.    Oonk, Synthesis of strontium and barium cerate and their reaction    with carbon dioxide, Solid State Ionics, vol. 61, p. 83-91 (1993);-   S. V. Bhide and A. V. Virkar, Stability of AB _(1/2) ′B _(1/2) ″O    ₃-type mixed perovskite proton conductors, Journal of the    Electrochemical Society, vol. 146(12), p. 4386-4392 (1999);-   G. Karagiannakis, S. Zisekas and M. Stoukides, Hydrogenation of    carbon dioxide on copper in a H+ conducting membrane-reactor, Solid    State Ionics, vol. 162-163, p. 313-318 (2003);-   N. Zakowsky, S. Williamson and J. T. S. Irvine, Elaboration of CO ₂    tolerance limits of BaCe _(0.9) Y _(0.1) O _(3-α) electrolytes for    fuel cells and other applications, Solid State Ionics, vol. 176, p.    3019-3026 (2005);-   R. Hui, R. Maric, C. Deces-Petit, E. Styles, W. Qu, X. Zhang, J.    Roller, S. Yick, D. Ghosh, K. Sakata, and M. Kenji, Proton    conduction in ceria-doped Ba ₂ In ₂ O ₅ nanocrystalline ceramic at    low temperature, Journal of Power Sources, vol. 161, p. 40-46    (2006); and-   K. D. Kreuer, Aspects of the formation and mobility of protonic    charge carriers and the stability of perovskite-type oxides, Solid    State Ionics, vol. 125, p. 285-302 (1999).

Other protonic conductors also may be selected for use as electrolytesin the electro-hydrocarbon devices in accordance with the descriptionherein.

The anode of the electro-hydrocarbon devices may comprise variousmaterials. Platinum-based materials may be preferred for use as theanode in the electro-hydrocarbon devices.

The following exemplary list of materials may be used as anodes in theelectro-hydrocarbon devices described herein: platinum-ruthenium;platinum-iridium; IrO₂; and ultrafine IrO₂ powder combined withplatinum.

The following publications describing materials that may be useful asanodes in the electro-hydrocarbon devices are incorporated herein byreference in their entirety:

-   P. Millet, Water electrolysis using eme technology: electric    potential distribution inside a nafion membrane during electrolysis,    Electrochim. Acta, vol. 39(17), p. 2501-2506 (1994);-   K. Ledjeff, F. Mahlendorf, V. Peinecke and A. Heinzel, Development    of electrode/membrane units for the reversible solid polymer fuel    cell, vol. 40(3), p. 315-319 (1995);-   K. Onada, T. Murakami, T. Hikosaka, M. Kobayashi, R. Notu and K.    Ito, Journal of Electrochemical Society, vol. 149, A1069 (2002);-   E. Slavcheva, I. Radev, S. Bliznakov, G. Topalov, P. Andreev and E.    Budevski, Sputtered iridium oxide films as electrolysis for water    splitting via PEM electrolysis, Electrochemica Acta, vol. 52,    2007, p. 3889-3894 (2007); and-   T. Ioroi, N. Kitazawa, K. Yasuda, Y. Yamamoto and H. Takenaka,    Iridium oxide/platinum electrocatalysts for unitized regenerative    polymer electrolyte fuel cells, Journal of the Electrochemical    Society, vol. 147(6), p. 2018-2022 (2000).

Other materials also may be selected for use as anodes in theelectro-hydrocarbon devices in accordance with the description herein.

Selection of the particular type of material for use as the cathode,electrolyte, or anode in the electro-hydrocarbon devices describedherein may depend upon numerous factors. The following are exemplaryfactors one or more of which may be considered by one of skill in theart when selecting materials for use in the electro-hydrocarbon devicesdescribed herein depending on whether the material is to be used as thecathode, electrolyte, or anode:

the desired temperature, pressure, and electrical potential at which theelectro-hydrocarbon device is to operate;

the desired rate of reaction and reaction equilibrium point (i.e.maximum single-pass yield);

the material's resistance to poisoning, for example, by the adsorptionof reactants (e.g., carbon monoxide, carbon dioxide, water, andhydrogen), products (e.g. alcohols, oxygen, and hydrogen), reactioncontaminants or impurities (e.g., sulfur and ammonia), and inerts;

the material's cost;

the material's mechanical durability;

the material's coefficient of thermal expansion (e.g., how closely thecoefficients of the cathodic material and the anodic material are to thecoefficient of the electrolyte material);

whether or not the cathodic material and anodic material will undergo asolid state reaction with the electrolyte material;

the material's thermal stability (e.g., no dramatic phase changes overthe temperature range at which it operates and no interdiffusion ofconstituent elements between the cathode and electrolyte and between theanode and electrolyte);

the material's electronic or protonic conductivity;

the material's selectivity;

the material's resistance to the formation of reaction product layers;

the material's oxidative stability over a large range of oxygen partialpressures; and

the material's electro-catalytic activity (including, for example, thematerial's surface area, particle size, and dispersion of active sites).

One of skill in the art also may recognize and consult other factors inorder to select cathodic, anodic, and electrolyte materials for use inthe electro-hydrocarbon device. Exemplary desirable properties of theelectrolyte materials include the following: a specific ionicconductivity of greater than about 10⁻² S/cm to minimize resistivelosses (electrical conductivity not required); ionic conductivity over awide range of gaseous and liquid chemical compositions; chemicalstability; and thermodynamic stability when in contact with the cathodicand anodic materials. Exemplary desirable properties of the cathodic andanodic materials include the following: thermodynamic stability when incontact with the electrolyte; electrical conductivity; ionicconductivity; electro-catalytic activity; the ability to producethree-phase boundary structures; and tolerance to gaseous and liquidpoisons. Additionally, it is preferred that the cathodic, anodic, andelectrolyte materials have similar coefficients of expansion and highdimensional stability during fabrication of the electro-hydrocarbondevice.

The electro-hydrocarbon devices can be physically configured in variousfashions. Described herein are two exemplary configurations for thedevices.

FIG. 3 illustrates an exemplary physical configuration of anelectro-hydrocarbon device. In FIG. 3, the electro-hydrocarbon device300 is configured as a cylindrical unit. The cylinder wall has threelayers—the exterior anode 310, the electrolyte 320, and the interiorcathode 330. An electrical power source 340 is connected to the anode310 and cathode 330 by external circuit wiring 350, cathodicelectro-contact 361, and anodic electro-contact 352. A gaseous influent360 comprising at least one of carbon monoxide and carbon dioxide flowsthrough the interior of the cylinder, thus contacting the cathode 330.Water 380 in the form of a vapor, steam, or liquid travels across theexterior of the cylinder, thus contacting the anode 310. The electricalpower source 340 creates an electrical potential between the cathode 330and the anode 310 that drives the electrolysis of water to createhydrogen ions and liberate oxygen in effluent 390. The hydrogen ionstravel from the anode 310 through the electrolyte 320 to reach thecathode 330, where they react with carbon monoxide and/or carbon dioxideto create hydrocarbons in effluent 370.

Alternatively, the cathode and anode in FIG. 3 could be switched, aswell as the respective influent and effluent streams so that thatcathode is on the exterior of the cylindrical unit, the gaseous influentcontaining carbon monoxide and/or carbon dioxide contacts the exteriorcathode, the anode is on the interior of the unit, and thewater-containing influent contacts the anode on the interior of theunit.

FIG. 4 illustrates a second exemplary physical configuration of anelectro-hydrocarbon device. In FIG. 4, the electro-hydrocarbon device400 is configured as a plate-like unit. The plate has three layers—theanode 410, the electrolyte 420, and the cathode 430. An electrical powersource 440 is connected to the anode 410 and cathode 430 by externalcircuit wiring 450, cathodic electro-contact 451, and anodicelectro-contact 452. A gaseous influent 460 comprising at least one ofcarbon monoxide and carbon dioxide flows across the plate, thuscontacting the cathode 430. Water 480 in the form of a vapor, steam, orliquid flows across the opposite side of the plate, thus contacting theanode 410. The electrical power source 440 creates an electricalpotential between the cathode 430 and the anode 410 that drives theelectrolysis of water to create hydrogen ions and liberate oxygen ineffluent 490. The hydrogen ions travel from the anode 410 through theelectrolyte 420 to reach the cathode 430, where they react with carbonmonoxide and/or carbon dioxide to create hydrocarbons in effluent 470.

Although the electro-hydrocarbon devices illustrated in FIGS. 3 and 4are described in reference to a water-containing influent beingcontacted with the anode, it will be appreciated that thewater-containing influent instead could be substituted with a hydrogeninfluent. Use of a hydrogen influent may be desirable becauseelectrolysis of water would not have to be accomplished. However, use ofa hydrogen influent may be undesirable because of the cost associatedwith obtaining such an influent; use of a water influent allows directproduction of hydrogen, preferably using electricity from a renewableenergy source.

In order to maximize contact between the carbon monoxide and/or carbondioxide containing influent and the cathode, and contact between thewater-containing influent or hydrogen-containing influent and the anode,the influents preferable are made to be turbulent, for example, by theinclusion of random packing such as Raschig rings and other saddles,rings, balls, and so forth that induce turbulent flow of a fluid.Additionally, the flow rate with which the cathodic influents and anodicinfluents are delivered to, respectively, the cathode and anode may beadjusted in order to vary the contact that the influent has with itsrespective electrode.

The hydrocarbons that are produced at the electro-hydrocarbon device'scathode and the oxygen that is produced at the electro-hydrocarbondevice's anode are separated from each other by, in FIG. 3, thecylindrical cathode/electrolyte/anode body or, in FIG. 4, the planarcathode/electrolyte/anode body. For example, in FIG. 3 the alcohol exitsthe cathode at 370 whereas the oxygen exits the anode at 390. In FIG. 4the alcohol exits the cathode at 470 whereas the oxygen exits the anodeat 490. An arrangement where the effluent from the cathode and theeffluent from the anode are separated is highly desirable because mixingof the cathodic and anodic effluents may result in combustion of thehydrocarbons and oxygen given the low heat of combustion of lowerhydrocarbons and the temperatures at which the electro-hydrocarbondevices may operate.

The hydrocarbons produced at the cathode of the electro-hydrocarbondevice may be emitted from the device either as liquids or, because itmay be necessary to operate the device at temperatures high enough tovaporize the alcohol, as gases. If the hydrocarbons produced at thecathode of the electro-hydrocarbon device are emitted as gases, then thehydrocarbons subsequently can be condensed to a liquid as is commonlyknown in the art.

The devices of FIGS. 3 and 4 may be packaged as unit cells and connectedin a parallel fashion (e.g., a stacked array of unit cells) in order toform larger electro-hydrocarbon devices with increased processingcapacity.

A water electrolysis device may be designed similar to theelectro-hydrocarbon devices described herein and may be used to producehydrogen gas and/or hydrogen ions from a water-containing input. In anelectrolysis device, the cathodic, anodic, and electrolyte materials andthe device's operating conditions may be selected in a manner intendedto maximize the device's efficiency or ability to electrolyze water inorder to produce hydrogen gas and/or hydrogen ions. Preferably, theelectric power used to operate the electrolysis device is obtained froma renewable energy source. Accordingly, an electrolysis deviceconfigured similar to the electro-hydrocarbon devices described hereinand operating using electrical power from a renewable energy sourceprovides a process to store renewable energy in the form of hydrogen gasand provides a process to provide a renewable source of hydrogen fromthe electolysis of water. For example, a process for renewably producinghydrogen gas or hydrogen ions from a water-containing influent maycomprise: contacting a first influent with a cathode; contacting awater-containing influent with an anode connected to the cathode by anelectrolyte; and applying an electrical potential between the cathodeand the anode; wherein the electrical potential causes reduction of atleast a component of the first influent at the cathode and oxidation ofthe water-containing influent at the anode to produce hydrogen gas orhydrogen ions.

Combined Deoxygenation/Electro-Hydrocarbon Device

A combined deoxygenation/electro-hydrocarbon device also may be used forthe electrolytic production of hydrocarbons from gaseous, carbonaceousinfluents. The combined deoxygenation/electro-hydrocarbon device maycomprise a first input for accepting a gaseous influent, the gaseousinfluent comprising carbon dioxide gas; a second input for accepting aninfluent selected from the group consisting of water-containinginfluents and hydrogen-containing influents; a deoxygenation deviceconnected to the first input and that is capable of reducing at leastsome of the carbon dioxide gas in the gaseous influent to produce carbonmonoxide gas; and an electro-hydrocarbon device connected to thedeoxygenation device and the second input and that is capable ofreducing at least some of the carbon monoxide gas and any remainingcarbon dioxide gas to produce hydrocarbons.

The combined deoxygenation/electro-hydrocarbon device may be used toaccomplish a process comprising treating a gaseous influent comprisingcarbon dioxide gas with a deoxygenation device that is capable ofreducing at least some of the carbon dioxide gas in the gaseous influentto produce carbon monoxide gas; and treating the carbon monoxide gas andany remaining carbon dioxide gas with an electro-hydrocarbon device thatis capable of reducing at least some of the carbon monoxide gas and anyremaining carbon dioxide gas to produce hydrocarbons.

The deoxygenation device used in the combined device may be capable ofdeoxygenating a carbon dioxide-containing influent in order to producecarbon monoxide. The effluent of the carbon dioxide deoxygenation devicetherefore may comprise carbon monoxide, optionally with un-reactedcarbon dioxide. Alternatively, the deoxygenation device may bedeactivated in order to deliver a stream of gaseous carbon dioxidewithout producing carbon monoxide. Accordingly, the carbon dioxidedeoxygenation device may be used to provide a gaseous, carbonaceousinfluent of varying concentrations of carbon monoxide and/or carbondioxide that subsequently is used in the electro-hydrocarbon devicesdescribed herein.

The concentrations of carbon monoxide and/or carbon dioxide gases outputby the deoxygenation device may be varied, for example, by adjusting theelectric power delivered to the deoxygenation device (e.g., adjustingvoltage and/or amperage) and the residence time in the deoxygenationdevice of the reactants. For example, the deoxygenation device could beadjusted to reduce substantially all of the carbon dioxide in theinfluent to carbon monoxide, to reduce some of the carbon dioxide in theinfluent to carbon monoxide, or reduce substantially none of the carbondioxide in the influent to carbon monoxide. In this fashion thedeoxygenation device has the added benefit of enabling the delivery of avariable mixture of carbon dioxide and carbon monoxide to theelectro-hydrocarbon device. An optimal ratio of carbon monoxide andcarbon dioxide may be desirable, for example, because of evidence thatsuch optimization may reduce the activation energy of the reductionreaction that occurs in the electro-hydrocarbon device and increase theyield of hydrocarbon products from the electro-hydrocarbon device.

A deoxygenation device may comprise a deoxygenation cathode exposed to afirst input; a deoxygenation anode; a deoxygenation electrolyteconnecting the deoxygenation cathode and the deoxygenation anode; and adeoxygenation electrical power source connected to the deoxygenationcathode and to the deoxygenation anode.

The deoxygenation device may be useful for accomplishing a process fortreating a gaseous influent that comprises carbon dioxide gas. Theprocess comprises contacting the gaseous influent containing carbondioxide gas with a deoxygenation cathode connected to a deoxygenationanode by a deoxygenation electrolyte; and applying an electricalpotential between the deoxygenation cathode and the deoxygenation anodeto reduce at least some of the carbon dioxide gas to carbon monoxidegas.

FIG. 5 illustrates a deoxygenation device configured in a manner similarto the cylindrical electro-hydrocarbon device illustrated previously. InFIG. 5, the deoxygenation device 500 is configured as a cylindricalunit. The cylinder wall has three layers—the exterior anode 510, theelectrolyte 520, and the interior cathode 530. An electrical powersource 540 is connected to the anode 510 and cathode 530 by externalcircuit wiring 550, cathodic electro-contact 551, and anodicelectro-contact 552. A gaseous influent 560 comprising carbon dioxideflows through the interior of the cylinder, thus contacting the cathode530. The electrical power source 540 creates an electrical potentialbetween the cathode 530 and the anode 510 that drives the reduction ofcarbon dioxide to carbon monoxide at the cathode. The reduction ofcarbon dioxide at the cathode liberates oxygen ions that travel from thecathode 530 through the electrolyte 320 to reach the anode 510. At theanode 510, the oxygen ions bind to form oxygen gas that is expelled ineffluent 590. The effluent 570 of the electro-hydrocarbon deviceincludes, among other constituents, carbon monoxide (e.g., in the casewhere substantially all of the carbon dioxide in the influent is reducedto carbon monoxide), carbon dioxide (e.g., in the case wheresubstantially none of the carbon dioxide in the influent is reduced tocarbon monoxide), or a mixture of carbon monoxide and carbon dioxide(e.g, in the case where some of the carbon dioxide in the influent isreduced to carbon monoxide).

Alternatively, the cathode and anode in FIG. 5 could be switched, aswell as the respective influent and effluent streams so that thatcathode is on the exterior of the cylindrical unit, the gaseous influentcontaining carbon dioxide contacts the exterior cathode, the anode is onthe interior of the unit, and oxygen is expelled from the anode on theinterior of the unit.

A combined deoxygenation/electro-hydrocarbon device is depicted in FIG.6. The combined deoxygenation/electro-hydrocarbon device 600 comprises adeoxygenation device 620 and an electro-hydrocarbon device 650. Agaseous influent comprising carbon dioxide 610 enters the deoxygenationdevice 620 where some, all, or none of the carbon dioxide is reduced tocarbon monoxide. In a preferred embodiment, substantially all of thecarbon dioxide is reduced to carbon monoxide. Oxygen 630 is output fromthe deoxygenation device 620 as well as the stream 640 of carbonmonoxide and/or carbon dioxide. The stream 640 of carbon monoxide and/orcarbon dioxide subsequently is processed by the electro-hydrocarbondevice 650 as well as an influent 660 of water. The electro-hydrocarbondevice 650 outputs an alcohol-containing effluent 670 from its cathodeas well as an oxygen-containing effluent 680 from its anode. Again,although illustrated as having an influent of water 660, theelectro-hydrocarbon device 650 alternatively may have an influent ofhydrogen, in which case the electro-hydrocarbon device 650 would nothave an oxygen-containing effluent 680.

FIG. 7 illustrates an alternative configuration of a combineddeoxygenation/electro-hydrocarbon device 700. In FIG. 7, a parallelarray of deoxygenation devices 720 and a parallel array ofelectro-hydrocarbon devices 750 function in unison. Again, a gaseousinfluent comprising carbon dioxide 710 enters the array of deoxygenationdevices 720 where some, all, or none of the carbon dioxide is reduced tocarbon monoxide. In a preferred embodiment, substantially all of thecarbon dioxide is reduced to carbon monoxide. Oxygen 730 is output fromthe array of deoxygenation devices 720 as well as streams 740 of carbonmonoxide and/or carbon dioxide. The streams 740 of carbon monoxideand/or carbon dioxide subsequently are processed by the array ofelectro-hydrocarbon devices 750 as well as an influent 760 of water. Thearray of electro-hydrocarbon devices 750 outputs hydrocarbon-containingeffluent 770 from its cathodes as well as oxygen-containing effluent 780from its anodes. Again, although illustrated as having an influent ofwater 760, the array of electro-hydrocarbon devices 750 alternativelymay have an influent of hydrogen, in which case the array ofelectro-hydrocarbon devices 750 would not have an oxygen-containingeffluent 780.

The carbon dioxide gas that is processed by the deoxygenation devicesdescribed herein may be obtained from a variety of sources including,but not limited to, the atmosphere, industrial combustion processes, andsyngas. Like the gaseous influent described previously in regards to theelectro-hydrocarbon devices, the influent to the deoxygenation devicesmay be pre-treated in order to remove undesirable contaminants and/orinerts that might detrimentally affect the functioning of the devices.Poisoning may be caused, for example, by the irreversible adsorption ofspecies on the surface of the cathode/catalyst/electrocatalyst. Thus,contaminants and inerts that might poison the cathode or adsorb onto thecathode, thereby affecting the cathode's ability to catalyze thereduction of carbon dioxide to carbon monoxide, preferably may beremoved before the influent is passed into the deoxygenation devices.Such contaminants and inerts potentially include, but are not limitedto, heavy metals such as lead, iron, copper, zinc, and mercury;sulfur-containing species such as hydrogen sulfide and mercaptans;arsenic; amines; carbon monoxide (CO) in some instances; nitrogen (N₂);nitrogen oxides (NO_(x)); ammonia (NH₃); sulfur dioxide (SO₂); hydrogensulfide (H₂S); and so forth. The poisons hydrogen sulfide (H₂S), ammonia(NH₃), carbon monoxide (CO), and organic heterocyclic compoundscontaining nitrogen or sulfur may be especially strong in someinstances, and therefore preferably are removed from the influent. Thedegree to which contaminants may need to be removed from the influent,and the types of contaminants that may need to be removed, may bedependent upon the choice of electrocatalyst for use as the cathode aswell as the operating temperature and pressure of theelectro-hydrocarbon device.

The functioning of the deoxygenation device is described by thefollowing half-reactions:

Cathode: CO₂+2e ⁻

CO+O²⁻  (11.1)

Anode: O²⁻

½O₂+2e ⁻  (11.2)

Overall: CO₂

CO+½O₂  (11.3)

As seen in equation 11.1, at the cathode carbon dioxide is reduced tocarbon monoxide. The portion of the carbon dioxide influent that isreduced will depend upon the operating conditions of the deoxygenationdevice including, for example, the device's temperature and pressure,the voltage and amperage of the electrical current or potential appliedbetween the cathode and anode, the residence time in the reactor of thecarbon dioxide, the materials chosen for the device's cathode, anode,and electrolyte, and so forth. Accordingly, these parameters may beadjusted in order to achieve the desired operating profile of thedevice.

FIG. 8 illustrates the free energy verses enthalpy for the processtaking place in the deoxygenation device. As seen in FIG. 8 the freeenergy of the reaction is lower at higher temperatures. Accordingly, ahigher equilibrium conversion of carbon dioxide to carbon monoxide isattainable at higher temperatures. Therefore, the deoxygenation devicemay preferably operate at a temperature in the range from about 200° C.to about 1200° C. in order to maximize the single-pass conversion ofcarbon dioxide into carbon monoxide in the device. Additionally, thedeoxygenation device preferably operates at a pressure in the range fromless than about 1 atm to about 50 atm.

The cathode of the deoxygenation devices may comprise various materialsknown to catalyze the deoxygenation of carbon dioxide to carbonmonoxide. In particular, lanthanum-based catalysts are preferred for useas the cathode in the deoxygenation device. The following exemplary listof materials may be used as cathodes in the deoxygenation devicesdescribed herein: lanthanum strontium manganite (LSM); lanthanum calciamanganite (LCM); lanthanum strontium ferrite (LSF); lanthanum strontiumcobalt ferrite (LSCF); lanthanum strontium manganite (LSM)-ytrriastabilized zirconia (YSZ); lanthanum strontium (LSM)-gadolinium dopedceria (GDC); and lanthanum strontium cobalt ferrite (LSCF)-gadoliniumdoped ceria (GDC).

The electrolyte of the deoxygenation devices may comprise variousmaterials known to conduct oxygen ions. In particular, zirconia-basedoxygen ion conductors and doped ceria-based oxygen ion conductors arepreferred for use as the electrolyte in the deoxygenation device. Inregards to zirconia-based oxygen ion conductors, the following exemplarylist of materials may be used as electrolytes in the deoxygenationdevices described herein: ZrO₂—Y₂O₃; ZrO₂—Sc₂O₃; and ZrO₂—Yb₂O₃. Inregards to ceria-based oxygen ion conductors, the following exemplarylist of materials may be used as electrolytes in the deoxygenationdevices described herein: CeO₂—Gd₂O₃; CeO₂—Re₂O₃; CeO₂—Y₂O₃; andCeO₂—Sm₂O₃.

The anode of the deoxygenation devices may comprise various materialsknown to catalyze the deoxygenation of carbon dioxide to carbonmonoxide. Nickel-yttria stabilized zirconia (YSZ), nickel-gadoliniumdoped ceria (GDC), and ruthenium-yttria stabilized zirconia (YSZ) arepreferred materials for use as the anode in the deoxygenation devices.

Selection of the particular type of material for use as the cathode,electrolyte, or anode in the deoxygenation devices described herein maydepend upon numerous factors. The following are exemplary factors one ormore of which may be considered by one of skill in the art whenselecting materials for use in the deoxygenation devices describedherein depending on whether the material is to be used as the cathode,electrolyte, or anode:

the desired temperature, pressure, and electrical potential at which thedeoxygenation device is to operate;

the desired rate of reaction and reaction equilibrium point (i.e.maximum single-pass yield);

the material's resistance to poisoning, for example, by the adsorptionof reactants (e.g., carbon dioxide), products (e.g. carbon monoxide andoxygen), reaction contaminants or impurities (e.g., sulfur and ammonia),and inerts;

the material's cost;

the material's mechanical durability;

the material's coefficient of thermal expansion (e.g., how closely thecathodic material's and anodic material's coefficients are to thecoefficient of the electrolyte);

whether or not the cathodic material and anodic material will undergo asolid state reaction with the electrolyte;

the material's thermal stability (e.g., no dramatic phase changes overthe temperature range at which it operates and no interdiffusion ofconstituent elements between the cathode and electrolyte and between theanode and electrolyte);

the material's electronic or oxygen-ion conductivity;

the material's selectivity;

the material's resistance to formation of reaction product layers;

the material's oxidative stability over a large range of oxygen partialpressures;

and

the material's electro-catalytic activity (including, for example, thematerial's surface area, particle size, and dispersion of active sites).

One of skill in the art also may recognize and consult other factors inorder to select cathodic, anodic, and electrolyte materials for use inthe deoxygenation device. Exemplary desirable properties of theelectrolyte materials include the following: a specific ionicconductivity of greater than about 10⁻² S/cm to minimize resistivelosses (electrical conductivity not required); ionic conductivity over awide range of gaseous and liquid chemical compositions; chemicalstability; and thermodynamic stability when in contact with the cathodicand anodic materials. Exemplary desirable properties of the cathodic andanodic materials include the following: thermodynamic stability when incontact with the electrolyte; electrical conductivity; ionicconductivity; electro-catalytic activity; the ability to producethree-phase boundary structures; and tolerance to gaseous and liquidpoisons. Additionally, it is preferred that the cathodic, anodic, andelectrolyte materials have similar coefficients of expansion and highdimensional stability during fabrication of the electro-hydrocarbondevice.

Exemplary Uses of the Devices

The electro-hydrocarbon, deoxygenation, and combineddeoxygenation/electro-hydrocarbon devices are capable of providing manydivergent benefits. For example, the electro-hydrocarbon and combineddeoxygenation/electro-hydrocarbon devices may be used for the synthesisof hydrocarbons that have a wide variety of beneficial uses.

The devices described herein also may provide environmental benefitssuch as a reduction in atmospheric carbon dioxide levels by sequesteringcarbon dioxide from the atmosphere; slowing, stopping, or reversingglobal warming by reducing new emissions of carbon dioxide; and storingcarbon dioxide in a liquid fuel or in a plastic form. For example, theproduced hydrocarbons from the presently described reactions may bestored in a fuel container. For these purposes, the devices can be usedto accomplish a process comprising collecting carbon dioxide gas fromthe atmosphere; treating the carbon dioxide gas with a deoxygenationdevice that is capable of reducing at least some of the carbon dioxidegas in the gaseous influent to produce carbon monoxide gas; and treatingthe carbon monoxide gas and any remaining carbon dioxide gas with anelectro-hydrocarbon device that is capable of reducing at least some ofthe carbon monoxide gas and any remaining carbon dioxide gas to producehydrocarbons.

The combined deoxygenation/electro-hydrocarbon devices described hereinmay be used to sequester carbon dioxide from the atmosphere. Removal ofcarbon dioxide from the atmosphere is desirable in order to combat theeffects of global warming. It is estimated that the pre-IndustrialRevolution concentration of carbon dioxide in the atmosphere was about295 ppm by volume, compared to about 383 ppm by volume today.Accordingly, a reduction of about 88 ppm by volume of carbon dioxide isnecessary in order to return carbon dioxide levels to what they werebefore the Industrial Revolution. This corresponds to the removal ofapproximately 689.8 billion metric tons of carbon dioxide from theatmosphere, or about 23% of the current carbon dioxide in theatmosphere.

The theoretical minimum energy required for the isothermal recovery ofpure carbon dioxide from an impure atmosphere is given by the equation:ΔG=RT ln(P_(f)/P_(i)), where R is the gas constant, T is the temperatureat which the recovery takes place, P_(f) is the final partial pressure,and P_(i) is the initial partial pressure. Table 1 shows the estimatedcost for extraction of carbon dioxide from the atmosphere assuming anefficiency of about 80% and energy cost of $0.05/kWHr.

TABLE 1.0 estimated cost for extraction of CO₂ from atmosphere Temp(Celsius) Energy Cost $ per metric ton of CO₂ 0 7.0 20 7.6 50 8.3 1009.6 150 10.9 200 12.2 250 13.5 300 14.8 350 16.1 400 17.4 450 18.7 50020.0 550 21.2 600 22.5 650 23.8 700 25.1 750 26.4 800 27.7 850 29.0 90030.3

As Table 1 demonstrates, the cost of extracting carbon dioxide from theatmosphere increases with increasing operating temperature of theextraction system. Accordingly, extraction at ambient temperatures maybe desired in order to minimize the energy cost of the extraction.

The hydrocarbons obtained from sequestering carbon dioxide from theatmosphere may be stored, for example, as replacements for the strategicpetroleum reserves maintained by various countries including the UnitedStates. For example, the United States Department of Energy announced in2006 that it is expanding the strategic petroleum reserves byapproximately 1 billion barrels of oil, which is equivalent to about5.56×10¹² mega-joules (MJ) of energy. Assuming a release of about 72grams of carbon dioxide into the atmosphere for every MJ of energyproduced by the combustion of oil, this increase in strategic petroleumreserves alone has the potential to release about 0.4 billion metrictons of carbon dioxide into the atmosphere were it to be combusted.Accordingly, using hydrocarbons produced from carbon dioxide sequesteredfrom the atmosphere (such that there is no net increase in carbondioxide emissions when the hydrocarbons are combusted) would prevent theemission of an estimated 0.4 billion metric tons of carbon dioxide.

Sequestering carbon dioxide from the atmosphere using the devices andprocesses described herein has the additional benefit of storing carbondioxide that otherwise would be emitted to, or remain in, the atmospherein a liquid form. The liquid (i.e. the hydrocarbons) could be committedto long-term storage, for example, in underground salt caverns ascommonly is used to store petroleum reserves. Alternatively, the liquidhydrocarbons could be stored by domestic users, thus increasing domesticfuel storage reserves.

The devices described herein may be located, for example, near a givensource of carbon dioxide for conversion of the carbon dioxide tohydrocarbons. For example, a combined deoxygenation/electro-hydrocarbondevice may be located near a fossil fuel burning power plant. Thecombustion effluent from the power plant would be routed to thedeoxygenation portion of the device wherein some, all, or none of thecarbon dioxide may be reduced to carbon monoxide. The gaseous effluentthen would be passed through the electro-hydrocarbon portion of thedevice wherein at least some of the effluent from the deoxygenationportion of the device containing carbon monoxide and/or carbon dioxidewould be further reduced to form hydrocarbons. Preferably, thecombustion effluent would pass through a separation train to removeunwanted contaminants and inerts before being fed into the combineddeoxygenation/electro-hydrocarbon device. Another source of carbondioxide is Canada's natural gas reserves and the associated emissionsresulting therefrom.

The electro-hydrocarbon device, deoxygenation device, and combineddeoxygenation/electro-hydrocarbon devices described herein also may beused to slow, stop, or reverse global warming.

For example, in as much as the only source of carbon used to producehydrocarbons using the devices described herein is carbon dioxidesequestered from the atmosphere or some other source that is emittingcarbon dioxide into the atmosphere, there will be no net increase incarbon dioxide emissions to the atmosphere upon combustion of thehydrocarbons because the carbon dioxide emitted by combustion of thehydrocarbons is equal to the amount extracted from the atmosphere orrecovered from carbon dioxide-emitting sources.

Table 1.1 tabulates the recorded and estimated world energy consumptionof the primary fossil fuels oil, natural gas, and coal through the year2025.

TABLE 1.1 World Energy Consumption (quadrillion Btu) 1990 2000 2001 20052010 2015 2020 2025 Oil 135.1 155.9 156.5 164.2 181.7 200.1 219.2 240.7Natural Gas 75.0 91.4 93.1 103.0 117.5 137.3 158.5 181.8 Coal 91.6 93.695.9 100.7 110.9 119.6 128.1 139.0 Subtotal 301.7 340.9 345.5 367.9410.1 457.0 505.8 561.5

As seen in Table 1.1 for the year 2005, for example, approximately 164.2Quads of energy from the combustion oil were consumed, corresponding to,assuming 80 gm of carbon dioxide emitted per MJ of energy obtained fromoil combustion, about 13.86 billion metric tons of carbon dioxideemitted into the atmosphere. Approximately 103.0 Quads of energy fromthe combustion of natural gas were consumed, corresponding to, assuming56 gm of carbon dioxide emitted per MJ of energy obtained from naturalgas combustion, about 6.085 billion metric tons of carbon dioxideemitted into the atmosphere. Approximately 100.7 Quads of energy fromthe combustion of coal were consumed, corresponding to, assuming 100 gmof carbon dioxide emitted per MJ of energy obtained from coalcombustion, about 10.62 billion metric tons of carbon dioxide emittedinto the atmosphere. Thus, if the 367.9 Quads of energy obtained fromthe combustion of oil, natural gas, and coal in 2005 instead had beenobtained through the combustion of hydrocarbons made according to thedevices and processes described herein from carbon dioxide sequesteredfrom the atmosphere, approximately 30.6 billion metric tons of carbondioxide emissions may have been avoided.

The electro-hydrocarbon device, deoxygenation device, and combineddeoxygenation/electro-hydrocarbon devices described herein also may beused to store renewable energy. Renewable energy is energy derived fromresources that are regenerative or for all practical purposes cannot bedepleted. For this reason, renewable energy sources are fundamentallydifferent from the non-renewable fossil fuels that are the mostimportant modern energy source. Additionally, renewable energy sourcesdo not produce as many greenhouse gases and other pollutants as does thecombustion of non-renewable fossil fuel. Renewable energy sourcesinclude, for example, sunlight, wind, tides, and geothermal heat.

In order to store renewable energy, electrical power used in theelectro-hydrocarbon, deoxygenation, and combineddeoxygenation/electro-hydrocarbon devices can be provided by or derivedfrom a renewable energy source. Indeed, the electrical power sources ofthe deoxygenation devices and electro-hydrocarbon devices describedherein preferably utilize electricity from a renewable energy source.Use of renewable energy in these devices “stores” the renewable energyin the form of hydrocarbons produced using the devices. Thus, forexample, solar power or another renewable energy source can be used todrive the operation of an electro-hydrocarbon device that producesalcohols such as methanol and ethanol that in effect “store” therenewable electrical energy consumed in their production. Alcoholsprovide stable, dense, and readily accessible (e.g., by combustion)storage of energy from renewable sources.

Accordingly, an exemplary process for storing renewable energy comprisesproducing electrical energy from a renewable energy source and treatinga gaseous influent comprising at least one of carbon monoxide gas andcarbon dioxide gas with an electro-hydrocarbon device that is capable ofreducing at least some of the gaseous influent to produce hydrocarbons.The electro-hydrocarbon device utilizes the electric energy producedfrom the renewable energy source. In this exemplary device, the devicefor carrying out the process is an electro-hydrocarbon device whereinthe device is powered by electricity from a renewable energy source.

Additionally, the gaseous influent in the process described above forstoring renewable energy may be produced by treating carbon dioxide gaswith a deoxygenation device that is capable of reducing at least some ofthe carbon dioxide gas to produce carbon monoxide gas, and wherein thedeoxygenation device also utilizes electric energy produced from therenewable energy source. In this exemplary process, the device forcarrying out the process is a combined electro-hydrocarbon/deoxygenationdevice wherein both the electro-hydrocarbon and deoxygenation portion ofthe device is powered by electricity from a renewable energy source.

The electro-hydrocarbon and combined deoxygenation/electro-hydrocarbondevices further provide methods whereby stable, predictable globalenergy prices can be obtained for an extended, and possibly indefinite,time period. The methods achieve these goals by providing stable,renewable sources of combustion energy. According to these methods, thedevices may function as described herein using electrical energy fromrenewable energy sources to operate the devices. Perfectly efficientcombustion of hydrocarbons produced by the devices and methods, like thecombustion of other carbonaceous fuels, yields only carbon dioxide andwater. Because the devices operate by methods that are capable ofconsuming carbon dioxide and water, the devices and methods of theiroperation may be capable of recycling the combustion products of thehydrocarbons produced thereby, and thus may provide an indefinite supplyof combustion energy and more stable, predictable long-term globalenergy prices. Even in the event that perfectly efficient combustion ofhydrocarbons produced by the devices and methods is not achieved, carbondioxide and water are the predominant products of the combustion ofhydrocarbons, and therefore the devices and methods nevertheless providea very long-term, potentially indefinite, recyclable source ofcombustion energy. For example, a method to provide long-term, stableenergy prices may comprise the following: producing electrical energyfrom a renewable energy source; and treating a gaseous influentcomprising at least one of carbon monoxide gas and carbon dioxide gaswith an electro-hydrocarbon device that is capable of reducing at leastsome of the gaseous influent to produce hydrocarbons; wherein theelectro-hydrocarbon device utilizes the electric energy produced fromthe renewable energy source, and wherein the carbon monoxide and carbondioxide is obtained from the atmosphere.

The electro-hydrocarbon and combined deoxygenation/electro-hydrocarbondevices described herein are useful for the production of hydrocarbonsthat have a wide variety of uses.

For example, the alcohols produced using the devices may be used asfuels to supplement or replace gasoline, diesel, and other fossil fuels.The first four aliphatic alcohols (methanol, ethanol, propanol, andbutanol) in particular are of interest as fuels and fuel supplementsbecause they have characteristics which allow them to be used in moderninternal combustion engines. The generic formula for alcohols isC_(n)H_(2n+1)OH and the energy density of the alcohol increases withincreasing “n.” Heavier alcohols therefore may be preferred for use asfuel because of their higher energy density compared to lighteralcohols. Alcohols with energy densities comparable to the energydensities of currently used fossil fuels, however, may be especiallypreferred for use as replacement fuels and fuel supplements. Butanol,for example, has an energy density close to that of gasoline; thus it isparticularly well positioned for use as a gasoline replacement andsupplement. An exemplary use of alcohols to supplement fossil fuels andcombustion processes thereof is the injection of lighter alcohols suchas methanol into the air intake of combustion engines, and particularlyturbocharged and supercharged engines. Lighter alcohols such as methanolevaporate very quickly under the vacuum conditions in the air intake,thus cool the incoming air and providing denser air and increasedcombustion and energy output per cycle of the engine.

Another advantage of alcohol fuels compared to standard fossil fuel isthat alcohol fuels have higher octane ratings (i.e. knock-resistance)than do fossil fuels, thus allowing alcohol fuels to be used inhigher-compression, more efficient internal combustion engines. Andwhereas higher-compression engines burning fossil fuels have increasedNO_(x) emissions due to the fact that higher-compression engines operateat increased temperatures, alcohols such as ethanol require more energyto vaporize and combust, thus drawing energy out of the air andresulting in a lower temperature exhaust gas with concomitant decreasedNOx levels. Alcohol fuels, because they contain oxygen, also burn morecompletely than do traditional fossil fuels; for example, ethanolcombustion emits about half the carbon monoxide emitted by thecombustion of gasoline.

Alcohols produced using the devices described herein also may be used aschemical reagents or solvents in various chemical processes. Forexample, as reagents alcohols commonly are used in organic synthesis tocreate more other, typically more comples, molecules. For example,methanol is a starting material for the synthesis of the followingcompounds: formaldehyde, urea resins, phenol resins, melamine resin,xylene resin, paraformaldehyde resin, methane-di-isocyanate (MDI),butanediol, polyols, polyacetald, isoprene, hexamine, methyl tert-butylether (MTBE), acetic acid, ethanol, acetaldehyde, acetic anhydride,chloromethanes, methyl methacrylate (MMA), polymethyl methacrylate,methacrylates, coating resins, methyl formate, formamide, HCN, formicacid, methyl amines, dimethyl formamide (DMF), methylethanolamine,dimethylacetamide (DMAC), tetramethyl ammonium hydroxide (TMAH),carbonates, higher amines, dimethyl terephthlate (DMT),polyethyleneterephthalate (PET), dimethyl ether (DME), olefines,gasoline, hydrogen, carbon monoxide, single cell proteins, biochemicals,and others. Alternatively, the devices and process described herein maybe modified in order to allow compounds including, but not limited to,those listed above to be produced directly by the devices and processesdescribed herein. For example, the operating conditions, choice ofmaterial(s) for the catalyst, influents, and so forth may be adjusted inorder to allow the direct production by the devices and processesdisclosed herein of compounds other than alcohols, including compoundsfor which alcohols such as methanol and ethanol may act as startingmaterials such as those listed above but not limited thereto.

As solvents, alcohols also are used in organic syntheses; ethanol inparticular is useful because of its low toxicity and ability to dissolvenon-polar substances and often is used as a solvent in the synthesis ofpharmaceuticals, cosmetics, perfumes, and vegetable essences such asvanilla. The alcohols produced using the devices described herein alsomay be used as preservatives of biological specimens. Ethanol producedusing the devices further may be used as an antiseptic, for example todisinfect skin before injections are given and for the production ofethanol-based soaps. The alcohols produced using the devices describedherein also may be used as high-purity, medical-grade alcohols formedicinal uses. Preferably, the effluent of the electro-hydrocarbondevice comprises medical-grade alcohols; for example, operatingconditions of the device may be selected in order to producemedical-grade alcohols. If not, the electro-hydrocarbon device'seffluent may be further refined and purified in order to bring thealcohols to medical-grade purity.

The production of alcohols using the electro-hydrocarbon and combineddeoxygenation/electro-hydrocarbon devices and processes additionally isadvantageous because these devices and processes potentially may havereduced environmental impact compared to traditional industrialprocesses for the production of alcohols. For example, the production ofbioalcohols (or biofuels) from plant matter (e.g., soy and corn) harmsthe environment by encouraging the deforestation of land for use inagriculture (e.g., the widespread catastrophic deforestation of theAmazon in order to plant soy and corn crops used to produce biofuels),requiring high energy consumption to produce fertilizers used inagriculture, instigating water and land pollution from pesticides,fungicides, and herbicides used in agriculture, and so forth.

The above are only a small selection of the possible applications andconfigurations of the devices and processes that are envisioned. Manyother applications and configurations of the devices and processes alsoare possible in accordance with the description herein. The devices andprocesses therefore may be implemented in many suitable forms and thevarious steps and components may be functionally or physically varied tomeet the needs of different applications.

While the devices and process described herein have been described inthe context of the production of alcohols, it is appreciated that otheroxygenates and hydrocarbon compounds also may be produced using thedevices and processes herein.

It may be desirable to accomplish the synthesis of alcohols, includingethanol and methanol, using the electro-hydrocarbon devices and combineddeoxygenation/electro-hydrocarbon devices described herein at conditionsof relatively low temperature and pressure in order to reduce energycosts attendant with the operation of non-electrolytic syngas-basedsyntheses of alcohols at high temperature and pressure. Additionally,lower temperatures and pressures thermodynamically favor the reductionof carbon dioxide to form alcohols; thus, higher equilibrium conversionof carbon dioxide to alcohols is possible.

For example, methanol is synthesized from carbon dioxide at therelatively low temperature of about 170° C. and at the relatively lowpressure of about 8 Mpa over a ceria-supported palladium (Pd—CeO₂)cathode prepared via the co-precipitation method, achieving a one-passyield of about 92%. The high yield is capable of being obtained becausethe device is operated under more favorable thermodynamic conditions,namely, low temperature and pressure. An acceptable rate of reaction isobtained by applying electrical current or potential between the anodeand cathode in order to drive the migration of H⁺ ion across the anode,through the electrolyte, to the cathode. Without the application ofelectrical current or potential, the reaction rate would be too slow forindustrial purposes. Because of the application of electrical current orpotential, traditional reaction conditions of approximately 300° C.temperature is avoided even while acceptable reaction rates areobtained.

In addition to removing or sequestering or harnessing carbon dioxide gasfrom the atmosphere, industrial source, or another source, any othersource of carbon may be employed. If the carbon source is not carbondioxide and/or carbon monoxide, it may be traditional sources of carbon,such as fossil fuels, coal, peat, oil and methane clathrates, and otherhydrocarbons.

If the carbon source is carbon dioxide gas, several methods of obtainingthe gas and pretreating the gas before reaction may be employed, such asto be described below, including, an extraction unit, a plasma energytreatment step, a deoxygenating step, and combinations thereof.

The hydrogen source is preferably water or hydrogen gas. However, thehydrogen source is not so limited. It may include any combination ofhydrogen gas, water, ammonia, and hydrogen sulfide, and other suitablehydrogen containing compounds, such as simply hydrides, natural gas,fossil fuels, coal, peat, oil, alcohol, and emissions from bacteria andalgae. The hydrogen source may be pretreated before reaction, such as bythe method described, including a electrolysis step, a plasma energytreatment step, and other suitable steps.

The source of hydrogen is preferably water. It may enter the reactorafter a pretreatment step of electrolysis to form a combination ofhydrogen gas and water. The source of carbon is preferably carbondioxide gas sequestered from the atmosphere. It may enter the reactorafter a suitable pretreatment step through an electrolytic cellcontaining an anode and cathode. Inside the reactor, the catalyst isselected from known methods and procedures based on the desiredhydrocarbon. It is preferably, a ethanol or methanol favorable catalyst.The temperature and pressure within the reactor is preferably about lessthan 150° C. and less than about 3 atmosphere. The electricity suppliedto the reactor is preferably generated from a renewable energy source.The reactor may be a small sized reactor such that it fits within acombustion engine. The reactor may also be scaled to industrial size.The resulting hydrocarbon is preferably methanol or ethanol.

A small sized reactor preferably uses about less than 10 kWatt, suchthat the power source may be an electrical outlet found in a home. Alarge sized reactor may need several hundred megawatts of electricity.

CO₂ Extraction Unit

The device shown in FIG. 9 illustrates a carbon dioxide extraction unit.The carbon dioxide source 900, such as air enters the device andcontacts the anode 910. Potential runs between the anode 910 and cathode920. Exiting the extraction unit at 930 is the carbon dioxide gas. Theanode and cathode may be made of the materials described above.

Carbon dioxide sources can be subdivided into concentrated and dilutedstreams. Examples of concentrated CO₂ sources are natural CO₂ reservoirs(which contain up to 97% CO₂) and exhaust gases from a wide variety ofindustrial plants. Examples of the latter are plants for processing ofnatural gas, production of ethanol by fermentation and production ofbulk chemicals such as ammonia and ethylene oxide. Also important is theinorganic industry, notably for the production of cement.

The major sources of dilute CO₂ are flue gases from electric powergeneration, blast furnaces in steel making, exhaust gases from cars,trucks and buses. Electric power is the single largest source for CO₂emissions in industry. It contributes around 25% of the global CO₂emission and is forecasted to contribute to around 30% of global warmingby the year 2030.

Any suitable means, such as piping, conducts, suction and other meansmay be used in fluid communication with the carbon dioxide extractionunit 900 to provide the inlet carbon dioxide source 910.

The carbon dioxide exiting the unit 930 of FIG. 9 may be used in theelectrochemical hydrocarbon synthesis described above, such as in FIGS.3 and 4, i.e., the stream 930 may be routed into FIG. 3 at 360 or FIG. 4at 460. Although the processes described above may be used to producealcohols, said process are note limited to alcohols, and may be used toproduce any suitable hydrocarbon.

The present sources of CO₂ used in industry are displayed in Table 2.0.

TABLE 2.0 Present CO₂ Sources from Industry Industry Contribution %Ammonia Production 35 Oil and Gas Production 20 Geological Formations 20Ethanol Production 12 Chemicals Manufacturing 7 Flue Gases orCogeneration 3 Alcohol Production 2 Others 1

Electrolysis Thermodynamics

FIG. 10 illustrates a device for the electrolysis of water into gaseousoxygen and hydrogen, for the use of the resulting hydrogen to makehydrocarbons. Inlet source 1010 is water which enters device 1000. Exitstreams 1020 and 1030 are oxygen and hydrogen gases, respectively. Theproduction of hydrogen by the electrolysis of water consists of a pairof electrodes immersed in a conducting electrolyte dissolved in water. Adirect current is passed through the cell 1000 from one electrode to theother. Hydrogen is released at one electrode 1030 with oxygen evolved atthe other electrode 1020, and therefore water is removed from thesolution. In a continuously operating electrolysis cell, replacement ofpure water is required with a continuous stream of oxygen and hydrogenobtained from both electrodes. Since the basic electrolysis system hasno moving parts, it is reliable and trouble-free; and electrolysisrepresents the least labor-intensive method of producing hydrogen. Inaddition, electrolysis is an efficient method for generating hydrogenunder pressure. Increasing the pressure of operation of an electrolysiscell results in a higher theoretical voltage requirement for operation,but kinetically electrolysis cells run more efficiently at higherpressures; and the gain in efficiency typically offsets the extraelectrical energy required.

The device 1000 shown in FIG. 10 may be designed in a similar manner asthe devices shown in FIGS. 3 and 4. Device 1000 may be in a cylindricalunit like FIG. 3, or a plate unit as shown in FIG. 4. The anode,cathode, and electrolyte may be any of the above described.

A characteristic of electrolysis is not only that hydrogen and oxygenare produced from water, but that they are separated at the same time.However, this advantage is at the expense of having to utilizeelectrical energy; considered to be an expensive form of energy. Forthis reason electrolysis has been considered to be one of the moreexpensive methods for production of hydrogen. In comparison, it is theelectrical energy generation step that is expensive and inefficient;most commercial electrolyzers operate with electricity to hydrogenefficiencies of greater than 75%. Their capital cost potential is alsofar less than that of the power stations required to supply electricalenergy.

For a water electrolysis cell, it can be calculated that the voltagecorresponding to the enthalpy change, or the heat of combustion ofhydrogen is 1.47 volts at 25° C., whereas the cell voltage correspondingto the free energy change is only 1.23 volts.

In an ideal situation, 1.47 volts applied to a water electrolysis cellat 25° C. would generate hydrogen and oxygen isothermally, that is at100% thermal efficiency with no waste heat produced. However, it isimportant to illustrate that a voltage as low as 1.23 volts would stillgenerate hydrogen and oxygen, but the cell would absorb heat from itssurroundings.

In practical cells, there is usually an efficiency loss that is greaterthan the difference between the free energy voltage and the enthalpyvoltage. Therefore, operating cells usually operate at voltages greaterthan 1.47 volts and liberate heat due to various losses within the cell.The heat required to supply the entropy of reaction is thereforeprovided by some of this waste heat, and practical cells do not absorbheat from their surroundings. If an extremely well performing cell couldbe operated at below 14.7 volts, it would function as a refrigerator,drawing heat from its surroundings.

The free energy change voltage or “reversible voltage” varies withtemperature as shown in Tables 4.1 to 4.4 for H₂O, H₂S, and NH₃. Raisingthe temperature favors electrolysis since the electrode processesproceed faster with less losses due to polarization. For water, raisingthe temperature lowers the voltage at which water can be decomposed.With H₂S an increase in temperature actually raises the required voltagefor decomposition, however at temperatures above 200° C. sulphur becomespolymeric with increased viscosity, and therefore more difficult tohandle. On the other hand ammonia has negative free energy and istherefore spontaneous above 200° C., and would not require electricalinput.

Electrolyzer Operational Model

Electrolyzers are able to operate in either current mode or voltagemode. When operated in voltage mode, voltage is applied to theelectrolyser and depending on the operating conditions the electrolyserdraws current from the source. After a couple of cycles the electrolyserreaches a steady state value. This mode is suitable for when aphotovoltaic source is utilized. However, most commercially availableelectrolyzers run in current mode where the operating voltage of theelectrolyser is given by:

V _(electrolyzer) =E+V _(activation) +V _(Ohm)  (12.0)

where V_(electrolyzer) is the operating voltage of the electrolyser, Eis the open circuit voltage of the cell, V_(activation) is theactivation polarization and V_(ohm) is the Ohmic polarization. When aproton (H⁺) conducting membrane is utilized, for a water electrolyserthe following electrode reactions are applicable:

$\frac{\left. {H_{2}O}\leftrightarrow{{\frac{1}{2}O_{2}} + {2H^{+}} + {{2e^{-}\mspace{31mu} {Anode}} \oplus {2H^{+}}} + {2e^{-}}}\leftrightarrow{H_{2}\mspace{31mu} {Cathode}\mspace{11mu} \Theta} \right.}{\left. {H_{2}O}\leftrightarrow{H_{2} + {\frac{1}{2}O_{2}}} \right.}$

Similarly, when a proton (H⁺) conducting membrane is utilized for theelectrolysis of H₂S, the following electrode reactions are applicable:

$\frac{\left. {H_{2}S}\mspace{14mu}\leftrightarrow\mspace{14mu} {{\frac{1}{2}S_{2}} + {2H^{+}} + {{2e^{-}\mspace{31mu} {Anode}} \oplus {2H^{+}}} + {2e^{-}}}\mspace{14mu}\leftrightarrow\mspace{14mu} {H_{2}\mspace{31mu} {Cathode}\mspace{11mu} \Theta} \right.}{\left. {H_{2}S}\mspace{14mu}\leftrightarrow{H_{2} + {\frac{1}{2}S_{2}}} \right.}$

Again for the electrolysis of NH₃ when a proton (H⁺) conducting membraneis utilized, the following electrode reactions are applicable:

$\frac{\begin{matrix}\left. {NH}_{3}\leftrightarrow{{\frac{1}{2}N_{2}} + {3H^{+}} + {{3e^{-}\mspace{31mu} {Anode}} \oplus}} \right. \\\left. {{3H^{+}} + {3e^{-}}}\leftrightarrow{\frac{3}{2}H_{2}\mspace{34mu} {Cathode}\mspace{11mu} \Theta} \right.\end{matrix}}{\left. {NH}_{3}\leftrightarrow{{\frac{3}{2}H_{2}} + {\frac{1}{2}N_{2}}} \right.}$

In electrolysis, only the free energy of the reaction, ΔG, can beinterchanged with the electrical energy at constant temperature andpressure. The quantity of electric charge corresponding to the molarquantities in a balanced equation is equivalent to nF, where n is thenumber of electrons transferred per molecule and F is the Faraday value.If this quantity of electrical charge is transported through a potentialdifference of E volts, the amount of work required is given by nFE. Inan isothermal electrolysis unit at constant pressure and volume theGibbs free energy is given by:

ΔG=−nFE

Where E is the potential difference, or voltage. If ΔG is negative for aspontaneous cell reaction then E is taken as positive for aspontaneously discharging cell.

According to the Nernst equation, the open circuit voltage for anelectrolyser is given by:

$\begin{matrix}{E = {E^{o} - {\frac{2.303\; {RT}}{nF}{\log \left( \frac{p_{H_{2}}p_{O_{2}}^{1/2}}{a_{H_{2}O}} \right)}}}} & (13.0)\end{matrix}$

where E⁰ is the standard cell potential, R the gas constant, T the celltemperature, n is the number of electrons involved in the cell reaction(for water electrolysis n=2), F the faraday constant, p_(H) ₂ thepartial pressure of hydrogen, p_(O) ₂ the partial pressure of oxygen,and a_(H) ₂ _(O) is the water activity between the anode andelectrolyte—if a fuel cell is operated at below 100° C. where liquidwater is present then a_(H) ₂ _(O)=1. Therefore, it follows thatequation 14.0 becomes:

$\begin{matrix}{E = {E^{o} - {\frac{2.303\; {RT}}{2\; F}\log \; p_{H_{2}}} - {\frac{2.303\; {RT}}{4\; F}\log \; p_{O_{2}}}}} & (14.0)\end{matrix}$

In Tables 2.1 to 2.3 the effect of partial pressures of reactants andproducts on the cell voltage of electrolysis cells for the dissociationof H₂O, H₂S and NH₃ are given. It is apparent for H₂O electrolysis thatas the pressure is increased the voltage source will need to provide ahigher voltage for the cell reaction to occur. An increase in pressurefrom 1 atm to 10 atm results in a decomposition voltage 44 mV higher.The energy required to provide this additional is equal to the potentialenergy contained in the high-pressure hydrogen. In practice waterelectrolyzers operate somewhat closer to ideal at higher pressures thanthey do at atmospheric pressure, that is the efficiency losses are lessat higher pressures. This is do to various reasons, including that thegas bubbles emitted are smaller in size and provide less hindrance tothe passage of ionic current across the cell. The energy requirements ofa practical electrolyser are always greater than the minimum theoreticalenergy requirements. Efficiency losses occur due to the following:

the resistance of the electrolyte itself (i.e. ohmic losses);

concentration polarization (change in the electrode voltage) due tochanges in the concentration of hydrogen ions, oxygen ions, or water inthe vicinity of the electrodes;

activation polarization—voltage gradients set up at theelectrode-electrolyte interface due to the slowness of the electrodereactions; and

in addition, there are small losses in the electronic conduction ofcurrent through the metallic conductors within the cell.

The voltage efficiency of an electrolyser or electrochemical system is afunction of the applied current, decreasing as the current is increased.When the operating voltage is plotted against the current per unit areaof electrode (current density) a characteristic curve, otherwise knownas a polarization curve is obtained. Polarization curves show therelationship between the voltage (voltage efficiency in an electrolyser)and current density for an electrochemical system. By doubling thecurrent density, and therefore doubling the rate of hydrogen production,the effective capital cost of the cell is halved, although theefficiency is reduced. The polarization curve can be used to determinethe optimum operating conditions according to capital cost andefficiency in relation to operating profit. The critical economic andtechnical factors which determine the operating conditions of anelectrochemical system consist of: cost of electricity (either consumedor produced); cost of feed stock materials (H₂O, NH₃, H₂S, CO₂, H₂,etc.); value in products (H₂, Alcohols, Ethers, Alkanes, Alkynes, etc.);cost of equipment; and lifetime of components.

TABLE 2.1 Effect of pressure on Cell Voltage for H₂O Electrolysis CellEmf P_(O2) P_(H2) −1.202 0.25 0.25 −1.216 0.5 0.5 −1.229 1 1 −1.242 2 2−1.260 5 5 −1.273 10 10 −1.287 20 20

TABLE 2.2 Effect of pressure on Cell Voltage for H₂S Electrolysis CellEmf P_(H2) P_(S2) P_(H2S) −0.3704 0.25 0.25 0.25 −0.3748 0.5 0.5 0.5−0.3793 1 1 1 −0.3837 2 2 2 −0.3896 5 5 5 −0.3941 10 10 10 −0.3985 20 2020

TABLE 2.3 Effect of pressure on Cell Voltage for NH₃ ElectrolysisE(Pressurized) PN₂ PH₂ PNH₃ −0.0448 0.25 0.25 0.25 −0.0508 0.5 0.5 0.5−0.0567 1 1 1 −0.0626 2 2 2 −0.0705 5 5 5 −0.0764 10 10 10 −0.0824 20 2020

NH₃ Electrolysis

To overcome the difficult storage of hydrogen, several carriersconsisting of alcohols, hydrocarbons, ammonia, etc. may be used insteadof water as the source 1010 entering the device shown in FIG. 10. Inmany ways ammonia is an excellent hydrogen carrier; liquid ammoniarepresents a convenient means of storing hydrogen, boasting a specificenergy density of 11.2 MJ/dm³ versus 8.58 MJ/dm³ for liquid hydrogen.Ammonia is easily condensed at ambient temperature (at 8 bar ofpressure) which makes it suitable for transportation and storage.Despite ammonia being flammable within the defined limits of 16-25% byvolume in air and toxic (above 25 ppm) its presence can be detected byits characteristic odor above 5 ppm. Ammonia is produced in largequantities (greater than 100 million ton/year) which indicates economyof scale in the cost of production. For these reasons NH₃ may be acommercial source of hydrogen. The decomposition of ammonia byelectrochemical methods in alkaline media at low overpotentials isNO_(x) and CO_(x) free with nitrogen and hydrogen as products of thereaction.

According to the following series of reactions ammonia is converted intonitrogen and hydrogen gas within an alkaline based electrolyser, i.e.OH⁻ being the ionic carrier, according to:

$\begin{matrix}\left. {{2{{NH}_{3}({aq})}} + {6{OH}^{-}}}\leftrightarrow{{N_{2}(g)} + {6H_{2}O} + {6e^{-}}} \right. & (14.0) \\\underset{——————————————————————————}{\left. {{6\; H_{2}O} + {6e^{-}}}\leftrightarrow{{3{H_{2}(g)}} + {6{OH}^{-}}} \right.} & (14.1) \\{\mspace{85mu} \left. {2{{NH}_{3}({aq})}}\leftrightarrow{{N_{2}(g)} + {3{H_{2}(g)}}} \right.} & (214.2)\end{matrix}$

The theoretical energy consumption during ammonia electrolysis is equalto 1.55 Whr/gm H₂ compared to the electrolysis of water at 33 Whr/gmH₂O. This is a 95% lower energy cost than water electrolysis. Thistechnology possesses scalability as well as the ability to easilyoperate in an on-demand mode facilitates the technology's ability tointerface with renewable energy including intermittent sources derivedfrom wind and solar energy.

Ammonia can be electrochemically decomposed to yield hydrogen, inaccordance with known techniques. Several experimental variables existin the electrolytic decomposition of ammonia. These variables consist ofthe pH and the chloride ion in solution, the type of anodesutilized—either IrO₂, RuO₂ or Pt. In addition, changes in currentdensity and the initial ammonia concentration affect the efficiency ofthe decomposition. The best electrode was determined to be RuO₂ in bothacidic and alkali conditions due to the generation of large quantitiesof OH radicals (note: during plasma dissociation of H₂O at 3473K, 0.1509atm of OH is produced—this may be advantageous for the decomposition ofNH₃).

Electrochemical Hydrocarbon Synthesis

Carbon dioxide is one of the cheapest and most abundant carbon based rawmaterials in the world. Unfortunately, CO₂ is rather inert and most ofits reactions are energetically unfavorable. Development of a goodcatalyst provides a means of reacting CO₂. However, the secondlimitation is in relation to thermodynamics and is not solvable byadvanced catalysis. In Tables 3.1 to 3.4 a listing of reactions with COand CO₂ for both exothermic and endothermic processes is provided. Intraditional processes the exothermic processes are extremely sensitivedue to deactivation of the catalyst from localized overheating. Thesynthesis processes described herein can control this phenomena and toprevent it from occurring.

The processes in Table 3.1 which are spontaneous (i.e. −ΔG⁰) andexothermic) (−ΔH⁰) occur without an input in energy; however therequired H₂ does require energy in its formation. The free energy of areaction is given by: ΔG⁰=ΔH⁰−TΔS⁰ where ΔH⁰ is the enthalpy of thereaction (or heat produced or consumed) and ΔS⁰ is the entropy or changein order or disorder occurring in a reaction.

In general, the reaction of H₂ to H₂O contributes to the negative orslightly positive free energies of these reactions. Reactions which arehighly exothermic pose the most trouble in deactivation ofcatalyst/electro-catalyst. All energy figures are in kJ/mol unless notedotherwise.

TABLE 3.1 Enthalpy and Free Energy for Exothermic Reactions InvolvingCarbon Dioxide Substance Reaction ΔH° ΔG° Formic Acid CO₂(g) + H₂(g)  

  HCOOH(l) −31.0 +34.3 Formaldehyde CO₂(g) + 2H₂(g)  

  HCHO(g) + H₂O(l) −11.7 +46.6 Methanol CO₂(g) + 3H₂(g)  

  CH₃OH(l) + H₂O(l) −137.8 −10.7 Methane CO₂(g) + 4H₂(g)  

  CH₄(g) + 2H₂O(l) −259.9 −132.4 Oxalic Acid 2CO₂(g) + H₂(g)  

  (COOH)₂(l) −39.3 +85.3 Ethylene 2CO_(2(g)) + 2CH_(4(g))  

  C₂H_(4(g)) + 2H₂O_((l)) −189.7 −208.3 Dimethyl Ether 2CO_(2(g)) +6H_(2(g))  

  CH₃OCH_(3(g)) + 3H₂O_((l)) −264.9 −38.0 Methyl Formate CO₂(g) +H₂(g) + CH₃OH(l)  

  HCOOCH₃(l) + H₂O(l) −31.8 +25.8 Acetic Acid CO₂(g) + H₂(g) + CH₃OH(l) 

  CH₃COOH(l) + H₂O(l) −135.4 −63.6 Ethanol CO₂(g) + 3H₂(g) + CH₃OH(l)  

  C₂H₅OH(l) + 2H₂O(l) −221.6 −88.9 Methanamide CO₂(g) + H₂(g) + NH₃(g)  

  HCONH₂(l) + H₂O(l) −103.0 +7.2 Acetic Acid CO₂(g) + CH₄(g)  

  CH₃COOH(l) −13.3 +58.1 Acetaldehyde CO₂(g) + CH₄(g) + H₂(g)  

  CH₃CHO(l) + H₂O(l) −14.6 +74.4 Acetone CO₂(g) + CH₄(g) + H₂(g)  

  CH₃CHO(l) + H₂O(l) −70.5 +51.2 Acrylic Acid CO₂(g) + C₂H₂(g) + H₂(g)  

  CH₂═CHCOOH(l) −223.6 −115.0 Acrylic Acid CO₂(g) + C₂H₄(g)  

  CH₂═CHCOOH(l) −49.1 +26.2 Propanoic Acid CO₂(g) + C₂H₄(g) + H₂(g)  

  C₂H₅COOH(l) −166.1 −56.6 Propionaldehyde CO₂(g) + C₂H₄(g) + 2H₂(g)  

  C₂H₅CHO(l) + H₂O(l) −171.1 −44.4 Benzoic Acid CO₂(g) + C₆H₆(l)  

  C₆H₅COOH(l) −21.6 +30.5 CO₂(g) + C₆H₅OH(l)  

  m-C₆H₄(OH)COOH(l) −6.6 +46.9

In Table 3.2 the reactions listed are non-spontaneous and endothermic,since there is an absence of hydrogen and its subsequent conversion towater. However, this is not a concern with our modular based hydrocarbonsynthesis unit. The energy required for all the reactions listed inthese Tables 3.1 to 3.4 can be added via electrochemical orelectro-catalytic processes, plasma activated gas phases, or plasmaenhanced electrochemical systems at lower operating temperatures andover a wider range of pressure than traditional processes.

TABLE 3.2 Enthalpy and Free Energy for Endothermic Reactions InvolvingCarbon Dioxide Substance Reaction ΔH° ΔG° Ethylene Oxide CO₂(g) +CH₂═CH₂(g)

 CH₂CH₂O(l) + CO(g) +152.9 +177.3 Carbon Monoxide CO₂(g) + C(s)

 2CO(g) +172.6 +119.9 Methane Reform. CO₂(g) + CH₄(g)

 4CO(g) + 2H₂O(l) +235.1 +209.2 Methane Reform. CO₂(g) + CH₄(g)

 2CO(g) + 2H₂(l) +247.5 +170.8 Ethane 2CO₃(g) + 2CH₄(g)

 C₂H₆(g) + CO(g) + H₂O(l) +58.8 +88.0 Ethylene Oxide CO₂(g) + C₂H₄(g)

 C₂H₄O(g) + CO(g) +178.0 +176.0

In Table 3.3 a series of exothermic reactions for CO combined withhydrogen are listed. Again H₂ and its conversion to H₂O contribute bothenthalpy (ΔH) and free energy (ΔG) to the overall thermodynamics ofthese reactions. The most efficient reaction is in the formation ofmethanol—none of the hydrogen is converted into water. In addition,methanol is an excellent building block for hydrocarbons includingdimethyl ether (DME).

TABLE 3.3 Enthalpy and Free Energy for Exothermic Reactions InvolvingCarbon Monoxide and Hydrogen Substance Reaction ΔH° ΔG° FormaldehydeCO(g) + H₂(g)  

  H₂CO(g) −5.4 27.2 Methanol CO(g) + 2H₂═CH₃OH(l) −131.6 −29.9 MethylKetene 2CO(g) + 2H₂(g)  

  CH₂CO(g) + H₂O(l) −125.9 −24.9 Acetylene 2CO(g) + 3H₂(g)  

  C₂H₂(g) + 2H₂O(l) −123.8 9.0 Methane CO(g) + 3H₂(g)  

  CH₄(g) + H₂O(l) −250.2 −150.9 Acetaldehyde 2CO(g) + 3H₂(g)  

  C₂H₄O(g) + H₂O(l) −231.0 −91.9 Ethanol 2CO(g) + 4H₂(g)  

  CH₃CH₂OH(l) + H₂O(l) −342.4 −137.7 Ethylene 2CO(g) + 4H₂(g)  

  C₂H₄(g) + 2H₂O(l) −298.1 −131.8 Ethyl group 2CO(g) + 9/2H₂(g)  

  C₂H₅(g) + 2H₂O(l) −246.0 −68.7 Ethane 2CO(g) + 5H₂(g)  

  C₂H₆(g) + H₂O(l) −435.3 −233.0

In Table 3.4 a series of exothermic reactions for CO is listed for theformation of hydrocarbons. These reactions combine CO with moleculesother than H₂ to form hydrocarbons.

TABLE 3.4 Enthalpy and Free Energy for Exothermic Reactions InvolvingCarbon Monoxide Substance Reaction ΔH° ΔG° Formic Acid CO(g) + H₂O(s)  

  HCOOH(l) −24.8 +15.1 Oxalic Acid 2CO(g) + 2H₂O(l)  

  (COOH)₂(l) −26.9 +46.9 Methyl Formate CO(g) + CH₃OH(l)  

  HCOOCH₃(l) −25.6 +6.6 Acetic Acid CO(g) + CH₃OH(l)  

  CH₃COOH(l) −129.2 −82.8 Methanamide CO(g) + NH₃(g)  

  HCONH₂(l) −96.8 −12.0 Acrylic Acid CO(g) + C₂H₂(g) + H₂O(l)  

  CH₂═CHCOOH(l) −217.4 −134.2 Propionaldehyde CO(g) + C₂H₄(g) + H₂(g)  

  C₂H₅CHO(l) −164.9 −63.6Thermodynamics for H₂O, NH₃ and H₂S

Hydrogen Sources

Numerous sources of hydrogen are available for production ofhydrocarbons, alcohols, etc. They consist of H₂O, NH₃, H₂S, CH₄, etc.The thermodynamic data provides a guideline for determining the requiredcost in energy for dissociation of these materials. In Table 4.1 thedata for the dissociation of water is presented. It is apparent that anincrease in temperature will decrease the energy requirement ofelectricity in an electrolysis system.

TABLE 4.1 Dissociation of H₂O (liquid at 25° C.): H₂O 

 H₂ + O Temperature (° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 25 237,215285,835 163.155 200 220,415 243,573 48.959 400 210,273 245,410 52.209600 199,609 246,999 54.284

In Table 4.2 thermodynamic data for the dissociation of hydrogensulphide into hydrogen and elemental sulphur is provided. This is ahydrogen source that is easier to acquire according to thermodynamicsand is therefore less expensive than electrolysing water.

Sulphur is an abundant, multivalent non-metal with a melting point of115.2° C., and a boiling point of 444.6° C. It has a density of 1.819g/cm³ at its melting point but has the unusual phenomena of increasedviscosity above 200° C. due to the formation of polymeric chains.

TABLE 4.2 Dissociation of H₂S into S (Orthorhombic): H₂S 

 H₂ + S Temperature (° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 25 33,32220,499 −43.030 200 39,483 26,863 −26.680 400 43,766 32,154 −17.254 60046,655 36,106 −12.084

In Table 4.3 thermodynamic data for the dissociation of hydrogen sulfideinto hydrogen and diatomic sulphur is provided. Yet again this is ahydrogen source that is easier to acquire according to thermodynamicsand is therefore less expensive than electrolysing water.

TABLE 4.3 Dissociation of H₂S into S₂ (Orthorhombic): H₂S 

 H₂ + ½S₂ Temperature (° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 25 73,19584,800 38.945 200 65,908 86,663 43.880 400 56,791 88,388 46.949 60047,229 89,553 48.481Ammonia is an additional possibility and is in fact spontaneous athigher temperatures. Thermodynamic data for this decomposition isprovided in Table 4.4. Underlying these apparently favourablethermodynamics is the cost in producing ammonia. However, ammonia couldprove useful as a carrier of hydrogen, since the production of ammoniaworldwide is a large scale industrial process making ammonia readilyavailable.

TABLE 4.4 Dissociation of NH₃ (gaseous): NH₃ 

  3/2H₂ + ½N₂ Temperature (° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 2516,414 45,895 98.930 200 −1,811 49,396 108.259 400 −24,045 52,310113.455 600 −47,017 54,218 115.963

Another source of hydrogen is in the reforming of methane with water.This is presently the main source of hydrogen industrially due to itsspontaneous nature above temperatures of 800° C. It does requireconsiderable heat due to its endothermic nature, as shown in Table 4.5.This reformation would be easier and less demanding if it could beoperated at lower temperatures via a plasma enhanced and/orelectrochemical system, as described in the present invention.

TABLE 4.5 Reformation of CH₄ (gaseous): CH₄ + H₂O 

 CO + 3H₂ Temperature (° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 25 150,893250,175 333.161 200 102,848 213,634 234.222 400 54,740 219,950 245.483600 5,038 224,053 250.877 800 −45,419 226,416 253.341 1,000 −96,198227,487 254.269

FIG. 11 illustrates the reaction of gaseous carbon dioxide 1110 andhydrogen 1120 in an electro-hydrocarbon synthesis device 1130. An energysource may be supplied to the device 1130 and a catalyst may be used.Output from the device 1130 is any number of hydrocarbons 1140,including alcohols, esthers, alkanes, alkynes, and others. This device1130 may be physically designed in a similar manner to the devicesdescribed above, such as FIGS. 3 and 4. The input stream 1110 may be influid communication with the output stream of FIG. 9, 930. Any othersuitable source of carbon dioxide may be used. The input stream 1120 maybe in fluid communication with the output of device 1000, 1030. Anyother suitable source of hydrogen may be used in device 1130.

II. Production of Hydrocarbons Using Plasma Energy

In another embodiment of the invention one or both of the carbon sourceand hydrogen source may be treated with plasma energy prior to reactingthe influents together. The carbon source for the reaction may be anysuitable source of carbon, as described above, but is preferably carbondioxide.

The source of hydrogen is preferably hydrogen gas. It may enter thereactor after a pretreatment step of plasma treatment to create hydrogenions. The source of carbon is preferably carbon dioxide gas sequesteredfrom the atmosphere. It may enter the reactor after a suitablepretreatment step of plasma energy to produce carbon dioxide ions.Inside the reactor, a catalyst may be used. The anode, cathode, andelectrolyte as described in Section I may be used. The energy from thepretreatment plasma steps may be enough to carry the reaction throughwithout the need for high temperature and pressures and/or without theneed for the anode, cathode, and electrolyte. The temperature andpressure within the reactor is preferably about less than 150° C. andless than about 3 atmosphere. The electricity supplied to the reactor ispreferably generated from a renewable energy source and may be convertedinto ultrasonic or plasma energy prior to being applied to the reactor.The reactor may be a small sized reactor such that it fits within acombustion engine. The reactor may also be scaled to industrial size.The resulting hydrocarbon is preferably methanol or ethanol.

Plasma Dissociation of H₂O NH₃ and H₂S

Plasma States

Plasma states can be divided into two main categories: Hot Plasmas(near-equilibrium plasmas) and Cold Plasmas (non-equilibrium plasmas)Hot plasmas are characterized by very high temperatures of electrons andheavy particles, both charged and neutral, and they are close to maximumionization (i.e. 100%). Cold plasmas are composed of low temperatureparticles (charged and neutral molecular and atomic species) andrelatively high temperature electrons with low levels of ionization(10⁻⁴ to 10%). Hot plasmas include electrical arcs, plasma jets ofrocket engines, thermonuclear reaction generated plasmas, etc. Coldplasmas include low-pressure direct current (DC) and radio frequency(RF) discharges (silent discharges), discharges from fluorescent (neon)illuminating tubes. In addition corona discharges are also classified ascold plasmas.

The plasma state can be produced in the laboratory by raising the energycontent of matter regardless of the nature of the energy source. Plasmascan be generated by mechanical (close to adiabatic compression),thermally (electrically heated furnaces), chemically (exothermicreactions, e.g. flames), radiant sources (high energy electro-magneticand particle radiations, e.g. electron beams), nuclear (controllednuclear reactions), electrically (arcs, coronas, DC and RF discharges)and by a combination of mechanical and thermal energy (e.g. explosions).

High-temperature physical chemical processing via plasmas is applicableto: highly endothermic reactions; reactions limited at ordinarytemperatures because of slow reaction rates; reactions dependent onexcited states; reactions requiring high specific energy input withoutdilution by large volumes of combustion gases; and reactions or phasechanges to alter the physical properties of a material.

Some of the advantages of plasma processing include: rapid reactionrates; smaller apparatus; continuous rather than batch processing;automated control; and thermal processing.

Thermal processing is made up of at least two large categories ofphenomena; those of a purely physical nature and those involving one ormore chemical reactions. Physical processing involves heat transferbetween the plasma gas and the phase being treated, resulting in asubstantial increase in temperature with an associated physicaltransformation. Chemical processing involves one or more chemicalreactions induced in the condensed phase of the plasma itself.

Energy Consumption

One problem of applied plasma chemistry is the minimization of energyconsumption. Plasma chemical processes may consume electricity, arelatively expensive form of energy. Requirements for energy efficiencymay still be met when plasma technology is applied to such large-scaleapplications as chemical synthesis, fuel conversion, or emission controlof industrial and automotive exhaust gases.

Energy cost and energy efficiency of a plasma chemical process areclosely related to the chosen mechanism. The same plasma chemicalprocesses in different discharge systems or under different conditions(corresponding to different mechanisms) result in entirely differentexpenses of energy. For example, the plasma chemical purification of airwith small amounts of SO₂ using pulse corona discharge requires 50 to 70eV/mol. The same process stimulated under special plasma conditions byrelativistic electron beams requires about 1 eV/mol; therefore itrequires two orders of magnitude less electrical energy.

In Table 5.1 a listing of plasma sources and their associated operatingconditions is given. Of particular interest in our plasma processes isthe atmospheric plasma processes including glow discharge, streamer,dielectric discharge barrier (DBD) and microwave (MW). These processesare amenable to operation at atmospheric pressure which eliminatesexpensive vacuum pumping systems and provides higher gas densities andtherefore higher throughput.

Low-Pressure, Non-Equilibrium Cold Plasmas

Low-pressure, non-equilibrium cold plasmas are initiated and sustainedby DC, RF or microwave (MW) power transferred to a low-pressure gasenvironment with or without an additional electric or electromagneticfield. Ultimately, all these discharges are initiated and sustainedthrough electron collision processes due to the action of the specificelectric or electromagnetic fields. Accelerated electrons (energeticelectrons) induce ionization, excitation and molecular fragmentationprocesses leading to a complex mixture of active species, which willundergo, depending on the specific plasma mode (e.g. direct or remoteplasma environment), recombination processes in the presence or absenceof plasma. The recombination reaction mechanisms are different fromthose for conventional chemical processes.

TABLE 5.1 Summary of Plasma Parameters Parameter Arc Glow Streamer DBDFIW RF MW Pressure Up to 0.01 Torr- 0.1- 1 Torr- 0.01- 10⁻³- 0.1 Torr-10-20 atm 1 atm 1 atm 1 atm 200 Torr 100 Torr 1 atm Current (A) 0.25-10⁵10⁻⁴-10⁻¹ 10⁻⁴-10⁻³ 10⁻⁴-10⁻³ 50-200 10⁻⁴-10⁻¹ 0.1-1 Voltage(V) 10-700100-1,000 10-100 kV 1-10 kV 5-200 kV 500-5,000 V 0.1-10 kV E/N or E1-100 V/cm 10-50 V(cm 30-100 V(cm 30-100 V(cm 30-100 V(cm 10-100 V(cm1-1,000 V/cm Torr)⁻¹ Torr)⁻¹ Torr)⁻¹ Torr)⁻¹ Torr)⁻¹ T_(g), (K)3000-10000 300-600 300-400 300-600 300-400 300-1,000 300-6,000 T_(e)5000-10000 K 1-3 eV 1-3 eV 1-5 eV 1-10 eV 1-5 eV 1-5 eV N_(e), (cm⁻³)10¹⁵-10¹⁶ 10¹¹-10¹² 10¹¹-10¹² 10¹¹-10¹² 10¹¹-10¹³ 10¹¹ 10⁹-10¹⁷Uniformity in non-uniform uniform non-uniform non-uniform uniformUniform (low Uniform Space or uniform pressure) or (halo) & (atm)filamentary filamentary (high pressure) Main energy heating vibratoryElectricity electricity electricity Vibratory or Heating, inputelectricity vibratory or electricity

Due to the electrode, antenna and reactor geometries, their chemicalnature, their relative positions in the reaction chambers and also tothe individuality specificity of the processes (e.g. DC dischargesrequire electrodes with electrically conductive surfaces) plasmanon-uniformities can be variable.

Similar to the electrolytic reaction described in Section I, the plasmaenergy may be derived from an electrical energy source that is generatedfrom a renewable energy source, such as winder and/or solar.

Atmospheric-Pressure Plasma Technology

One industrial process operating close to atmospheric pressure includethermal plasmas which include electric arc furnaces and plasma torchesfor generation of powders, for spraying refractory materials, forcutting and welding and for destruction of hazardous waste. Theseapplications include the utilization of thermal plasmas close to localthermal equilibrium (LTE) and non-equilibrium (non-LTE) plasmas withelectron temperatures exceeding by orders of magnitude the temperaturesof heavy plasma components.

In a LTE type thermal plasmas all molecules are dissociated aredissociated and the molecular fragments are able to form new compounds.Plasmas offer a number of intrinsic advantages such as enhanced reactionkinetics, oxidizing or reducing atmospheres, high quenching rates andbetter control of chemical reactions.

Atmospheric pressure, non-LTE plasmas possess unique features that haveenabled several important applications. Electrons with sufficient energycolliding with a background gas can result in low levels ofdissociation, excitation and ionization without an appreciable increasein gas enthalpy. Non-LTE plasmas have electron temperatures which exceedthe temperature of heavy particles (atoms, molecules, ions) by orders ofmagnitude. Since the ions and neutrals remain relatively cold, theseplasmas do not cause thermal damage to the surfaces that they contactwith. This characteristic makes this type of plasma suitable forlow-temperature plasma chemistry and treatment of heat sensitivematerials including polymers and biological tissues. Examples of non-LTEplasmas are corona discharges, dielectric-barrier discharges (DBDs) andglow discharges.

Arc or corona discharges are initiated by partial breakdown of a gas gapin a strongly inhomogeneous electric field. The active ionization regionis restricted to a small volume around the active corona electrode of asmall radius of curvature, which is small in comparison with theinter-electrode distance. Typical configurations are pin-to-plane,wire-to-plane or a coaxial wire in a cylinder. There is a passive zoneof low conductivity which connects the active zone to the oppositeelectrode and stabilizes the low current discharge. The charge carriersin this drift region can be used to charge solid particles and dropletsor to induce chemical reactions. Examples of applications consist ofelectrostatic precipitators (ESPs) which are utilized for dustcollection in many industrial off gases. Recently DC arc dischargesoperating at low current (250 mA) and high voltage (700V) have beenobserved at atmospheric pressure, in air. Active stabilization wasrequired with a closed loop applied to current regulation of the powersupply.

DBD also referred to as barrier discharge or silent discharge consistsof an electrode configuration with at least one dielectric barrier(insulator) in the current path in addition to the gas gap used fordischarge initiation. At atmospheric pressure this type of discharge ismaintained by a large number of short-lived localized current filamentscalled micro-discharges. An example is in the generation ozone (O₃)utilizing optimized DBDs as utilized in water treatment and pulpbleaching. DBDs can operate at high power levels and can treat largeatmospheric-pressure gas flows with a negligible pressure drop—as usedin the treatment of air pollution for the decomposition of H₂S and NH₃.

The plasma of a glow discharge is luminous in contrast to a relativelylow-power dark discharge. A glow discharge is a self-sustainedcontinuous DC discharge having a cold cathode which emits electrons as aresult of secondary emission induced by positive ions. The classicaldischarge tube in a fluorescent lamp has been used for decades in theproduction of light. One Atmosphere Uniform Glow Discharge Plasma(OAUGDP), glow discharges operating at 1 atm will permit industrialprocesses that are otherwise uneconomical at 10 Torr pressure. TheOAUGDP is capable of a wide range of plasma processing tasks, as long asthe mean free paths are not required in the application. This plasmagenerates active species which are useful for sterilization,decontamination, and surface energy enhancement of films, fabrics, airfilters, metals and 3-D work pieces. Recently work has been performed inthe CO₂ reforming of CH₄ in the formation of synthesis gas with anatmospheric pressure glow discharge plasma. The experiments showed thatconversion of CH₄ and CO₂ was up to 91.9% and the selectivity of CO andH₂ was also up to 90%.

CO₂ Dissociation Products in Thermal Plasmas

Thermodynamically, the equilibrium composition of the CO₂ dissociationproducts in a thermal plasma depend only on temperature and pressure.This temperature dependence, is much stronger than pressure dependence.The main products of the plasma chemical process under consideration aregiven by:

CO₂→CO+½O₂ ΔH _(CO) ₂ =2.9 eV  (15.0)

Which are the saturated molecules CO and O₂. In addition, at very hightemperatures there is a significant concentration of atomic oxygen andcarbon.

Quenching is a post-reaction step, such that slow cooling could be quasiequilibrium, and reverse reactions would return the composition to theinitial reactant, i.e. CO₂. Fast cooling times in order of >10⁸ K/secwill result in production of CO as a product. In this situation atomicoxygen recombines into molecular oxygen faster than reacting with carbonmonoxide, thus maintaining the degree of CO₂ conversion. A maximumenergy efficiency of approx. 64% can be reached at 3000K with a highcooling rate of 10⁸ K/sec required.

The main dissociation products for H₂O consist of:

H₂O→H₂+½O₂ ΔH _(H) ₂ _(O)=2.6 eV  (15.1)

Which are the saturated molecules of H₂ and O₂. In contrast to CO₂,thermal dissociation of water vapour results in a variety of atoms andradicals. The concentration of O, H and OH are significant in thisprocess. Even when H₂ and O₂ are initially formed in thehigh-temperature zone are saved from reverse reactions, the activespecies O, H and OH can be converted into products (H₂ and O₂) or backinto H₂O. This qualitatively different behavior of radicals determinesthe key difference between the absolute and ideal mechanisms ofquenching.

Plasma Dissociation of H₂S

H₂S may be used as a source of hydrogen due its favorable dissociationthermodynamics. Water may also be dissociated. Chemical processes can beoperated in a plasma at temperatures up to 20,000 K and pressures from10 to 10⁹ Pascal. The high temperature generated by plasmas allows veryhigh conversion of thermodynamically limited endothermic reactions. Thevery high quenching rates of 10⁶ K/sec or higher are possible withplasma systems—assuring that a high conversion rate is possible.

The energy cost for plasma decomposition of H₂S was determined to bebetween 0.6 to 1.2 kWh/m3 and the H₂S could be pure or mixed with CO₂.It has been shown that using a corona discharge plasma reactor that H₂Scan be dissociated into H₂ and sulphur. However, due to high dielectricstrength of pure H₂S (approx. 2.9 times that of air) it was diluted withgases of lower dielectric strength to reduce the breakdown voltage.Regardless, it is entirely economically feasible to dissociate H₂S witha plasma system.

Plasma Assisted Catalysis

Plasma processes induce gas phase reactions—such as the generation ofacetylene from natural gas, or for the non-thermal activation viadielectric barrier discharges (DBDs) of low temperature processes likeozone generation. Catalytic processes can be very selective. Catalyticprocesses often require a specific gas composition and high temperature.One method of the invention combines plasma activation of reactions withthe selectivity of catalytic reactions.

Examples of such hybrid processes are plasma enhanced selectivecatalytic reduction (SCR) as performed in the reforming of methane tohydrogen and higher hydrocarbons. Hydrogen gas can be efficientlyproduced in plasma reformers from a variety of hydrocarbon fuels(gasoline, diesel, oil, biomass, natural gas, jet fuel, etc.) withconversion efficiencies close to 100%. Utilizing a gas discharge plasma,combined with a V₂O₅—WO₃/TiO₂ catalyst the pre-treatment of Dieselengine exhaust for the selective catalytic reduction (SCR) of NitricOxides has been performed. It is possible to produce synthesis gasthrough the conversion of methane using CO₂ in a dielectric barrierdischarge (DBD) with a catalyst consisting of Ni/γ-Al₂O₃. The productsproduced consisted of CO, H₂, C₂H₆, C₃H₈, and C₄H₁₀. In a similar mannermethane was converted directly to higher hydrocarbons (C₂H₂, C₂H₄, C₂H₆,C₃H₈, etc.) utilizing a Pt/γ-Al₂O₃ catalyst and dielectric-barrierdischarge. Methane activation via plasma is very effective becausemethyl radicals are easily formed—and which will induce various chemicalreactions. With plasma chemical reactions, free radicals control andmanipulation are important.

Catalysts/Electrocatalysts

This section discusses the catalytic reactions involving the oxidationof C₁-C₇ hydrocarbons and C₁-C₂ alcohols by carbon dioxide.

The largest consumers of CO₂ are the producers of carbamide (urea),calcined soda and salicylic acid. In all these industries CO2 isobtained not from the atmosphere but from secondary industrial gases andfrom solid carbonates (primarily from limestone). In 1995 the worldoutput of carbamide was 110 million tonnes annually. Carbamide is formedwhen CO₂ reacts with ammonia under a pressure of 200 atm at 200° C.according to:

2NH₃+CO₂

NH₄COONH₃+H₂O  (16.0)

Another major industry involving the use of CO₂ is the production ofcalcined soda, totaling about 30 million tones annually. Together withCO₂, the reactants are NaCl and ammonia according to:

NaCl+NH₃+CO₂+H₂O

NaHCO₃+NH₄Cl  (16.1)

Calcined soda is obtained by the heat treatment of NaHCO₃, whereupon CO₂and H₂O are evolved.

In 1990 the manufacture of salicylic acid followed by the production ofAspirin (acetylsalicylic acid) was 25,000 tons per year. The synthesisof salicylic acid is synthesized by carboxylating phenol under pressure(Kolbe-Schmidt reaction). This material is then reacted with aceticanhydride (CH₃CO₂O) to produce acetylsalicylic acid.

CO₂ is being utilized in the synthesis of organic carbonates. They areobtained by the interaction of oxiranes with CO₂ in the presence ofinorganic and organic halides. Organic carbonates are used as solventsand extractants, while polycarbonates are employed as constructionmaterials.

Dimethyl Ether (DME)

Dimethyl ether (DME) also known as methoxymethane, oxybismethane, methylether, and wood ether, is a colorless, gaseous ether with an etherealodor. DME gas is water soluble at 328 g/ml at 20° C. It has themolecular formula CH₃OCH₃ or C₂H₆O with a molecular mass 46.07 g/mol.The density of DME is 1.59 versus air and 668 kg/m³ as a liquid. Itsmelting point is −138.5° C. (134.6K) with a boiling point of −23° C.(254K)

DME is used as an aerosol spray propellant and combined with propane forcryogenic freezing. It is also used as a clean burning alternative toliquefied petroleum gas, liquefied natural gas, diesel and gasoline.Typically it is manufactured from natural gas, coal or biomass.

Dimethyl ether (DME) is used in producing gasoline, ethylene, aromaticand other chemicals. It is an alternative diesel fuel due to its low NOxemissions, near zero smoke and less engine noise. Traditionally, DME isproduced by methanol dehydration over catalysts, while methanol isproduced from synthesis gas (CO/H₂/CO₂). However, it is possible toproduce DME through a direct route called synthesis-gas-to-dimethylether (STD). This process is more thermodynamically and economicallyfavorable than the traditional route. The three major reactions in thisprocess consist of:

CO+H₂

CH₃OH  (16.2)

2CH₃OH

CH₃OCH₃+H₂O  (16.3)

CO+H₂O

CO₂+H₂  (16.4)

The methanol produced by reaction (6.3) is consumed by the dehydrationreaction (6.4), while the water formed in reaction (6.4) can react withCO through water gas shift reaction (6.5). This results in a dramaticincrease in conversion of CO. Typically, a mixed double-functioncatalyst is used in the STD process, composed of a methanol catalyst(Cu/Zn/Al, Cu/Zn/Cr or Cu/Zn/Zr) and a methanol dehydration catalyst(zeolite or γ-alumina).

For application within an electrochemical device reaction (16.5) and(16.6) are to be utilized as follows:

2CH₃OH

CH₃OCH₃+H₂O  (16.5)

CO+H₂O

CO₂+H₂  (16.6)

With the overall reaction consisting of:

2CH₃OH+CO

CH₃OCH₃+CO₂+H₂  (16.7)

As can be observed in reaction (16.7) as the ratio of CO/CO₂ increasesthe formation of dimethyl ether is favored. Through the utilization ofan oxygen anion (O²⁻) electrolyte, CO₂ will be reduced to CO—this beingelectrochemical and controlled externally. The CO/CO₂ mixture is thenreacted with methanol according to reaction (16.7).

In addition, the products of reaction (16.7) consisting of CO₂ and H₂can be utilized in the formation of methanol.

FIG. 12 illustrates a plasma device that accepts either carbon dioxidesource 1210 or hydrogen source 1210. If carbon dioxide is the source1210, output stream 1220 is an ionized mixture of carbon dioxide. If ahydrogen source 1210 is used, the output stream 1220 is ionizedhydrogen. The hydrogen source 1210 may be water, ammonia, or H₂S.Component 1230 illustrates the energy source, such as microwave, whilecomponent 1240 illustrates the plasma. The output streams may then berouted in fluid communication into a catalytic hydrocarbon synthesisdevice wherein the reactions described above would occur in the presenceof a suitable catalyst.

Source of CO₂ and CO

The production of Hydrocarbons, Alcohols, etc., requires a source of CO₂and CO which is derived from CO₂. Therefore, the CO₂ needs to bereformed into CO—there are several methods available, either chemically,electrochemically or through the use of plasma systems. In Table 6.1thermodynamic data for the dissociation of CO₂ to CO and O₂ is provided.As the temperature is increased the dissociation becomes more favorableand ultimately becomes spontaneous.

TABLE 6.1 Dissociation of CO₂ (gaseous): CO₂ 

 CO + ½O₂ Temperature (° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 25 257,287282,994 86.264 200 241,985 283,634 88.058 400 224,368 283,558 87.950 600206,838 283,067 87.319 800 189,447 282,356 86.589 1,000 172,202 281,51085.867 2,000 87,896 276,463 82.959 3,000 5,940 271,318 81.081 4,000−74,457 266,450 79.782 5,000 −153,726 261,761 78.795 6,000 −232,118257,291 78.018

In Table 6.2 the dissociation of CO₂ and associated species is projectedto typical plasma temperatures. It is apparent as the temperatureincreases more reactive species such as monotonic oxygen (O) and ozone(O₃) increase in concentration. There is also a wide range of typicalplasma species (not listed in the Tables) consisting of radicals (highlyreactive), electrons, etc. Understanding the intermediate reactionsequences for the required overall chemical hydrocarbon formationreactions be it chemically, electrochemically with or without plasmaenhancement, it would be possible to tailor the composition of theplasma gases to optimize these reactions. In Tables 6.3 to 6.5 data forplasma gas compositions CO₂, H₂S, H₂O, and NH₃ at temperatures from1,000 to 6,000° C. is provided.

TABLE 6.2 Plasma Dissociation of CO₂ (gaseous) CO₂ → Various SpeciesTemp. (° C.) CO₂ (atm) CO (atm) O₂ (atm) O (atm) O₃ (atm) 1,000 0.999960.00002454 0.00001227 3.7447 × 10⁻¹⁰ 1.5343 × 10⁻¹⁷ 2,000 0.918890.053845 0.02658 0.00068621  6.440 × 10⁻¹⁰ 3,000 0.46649 0.24435 0.177320.11185 0.11821 4,000 0.011493 0.51098 0.03345 0.44408 3.3846 × 10⁻⁰⁸5,000 0.0007739 0.50031 0.0026575 0.49584  1.627 × 10⁻⁰⁹ 6,000 0.00013160.4673 0.00043024 0.51026 1.7589 × 10⁻¹⁰

TABLE 6.3 Plasma Dissociation of H₂S (gaseous) H₂S → H₂ + S Temp. (° C.)H₂S (atm) H₂ (atm) S₂ (atm) H₂S₂ (atm) HS (atm) H (atm) 1,000 0.724310.18159 0.086705 0.0061184 0.00071279 3.0208 × 10⁻⁷ 1,500 0.276640.47478 0.23199 0.001881 0.013581 0.00019497 2,000 0.093205 0.572380.27087 0.0004408 0.0484 0.0063229 3,000 0.009808 0.37997 0.126880.000017682 0.087563 0.020898 4,000 0.0001795 0.057064 0.0089684 5.6769× 10⁻⁰⁸ 0.0016606 0.59091 5,000 0.000003623 0.0059452 0.00089709 2.5958× 10⁻¹⁰ 0.0024428 0.65852 6,000 2.1944 × 10⁻⁷ 0.0011192 0.000184055.3568 × 10⁻¹² 0.00060859 0.66509

TABLE 6.4 Plasma Dissociation of H₂O (gaseous) H₂O → H₂ + ½O₂ Temp. (°C.) H₂O (atm) H₂ (atm) O₂ (atm) OH (atm) H (atm) O (atm) 1,000 0.999970.000018044 8.527 × 10⁻⁶ 1.984 × 10⁻⁶ 3.011 × 10⁻⁹ 3.122 × 10⁻¹⁰ 2,0000.96224 0.019522 0.0075883 0.009115 0.001168 0.0003667 3,000 0.415710.17962 0.059074 0.1373 0.1437 0.06456 3,100 0.33136 0.1866 0.0603980.14692 0.18825 0.086371 3,200 0.25312 0.18655 0.059371 0.15087 0.023850.11150 3,300 0.3161 0.17924 0.056037 0.14851 0.29239 0.13899 3,4000.12872 0.16556 0.05077 0.14016 0.34726 0.1647 3,500 0.08572 0.147280.044216 0.12704 0.4003 0.1954 4,000 0.007104 0.055203 0.014439 0.0502850.58119 0.29176 5,000 0.00005546 0.0059296 0.0011745 0.005512 0.657660.32963

TABLE 6.5 Plasma Dissociation of NH₃ (gaseous) NH₃ → ½N₂ + 3/2H₂ Temp.(° C.) NH3 (atm) H₂ (atm) N₂ (atm) H (atm) N (atm) NH (atm) 298 0.938080.046443 0.015481 4.999 × 10⁻³⁷ negligble 2.9882 × 10⁻⁶⁷  473 0.148570.63857 0.21286 2.724 × 10⁻³⁷ 3.132 × 10⁻⁵⁰  1.081 × 10⁻⁴¹ 673 0.0087230.74670 0.24890 4.752 × 10⁻¹⁵ 1.243 × 10⁻³⁴   2.88 × 10⁻²⁹ 873 0.00099730.74963 0.24988 4.026 × 10⁻¹¹ 3.534 × 10⁻²⁶  1.428 × 10⁻²² 10730.0001222 0.74991 0.24997 1.206 × 10⁻⁸  7.263 × 10⁻²¹  2.254 × 10⁻¹⁸2,273 0.00000451 0.74369 0.24910  0.0072073 1.435 × 10⁻⁸  1.059 × 10⁻⁸3,273 0.00000111 0.53335 0.21903 0.24758  3.25 × 10⁻⁵ 3.726 × 10⁻⁶ 4,2734.4736 × 10⁻⁸ 0.092178 0.15500 0.75102 1.7627 × 10⁻³   3.358 × 10⁻⁵5,273  1.093 × 10⁻⁹ 0.009598 0.13165 0.83672 0.021962 7.568 × 10⁻⁵ 6,273  5.324 × 10⁻¹¹ 0.0016612 0.083181 0.81028 0.10477  1.003 × 10⁻⁴

Interaction of Carbon Dioxide with Hydrogen

Hydrogen is an excellent reductant for carbon dioxide. Thethermodynamics for the most important reactions of CO₂ with hydrogen andassociated reactions are provided in Tables 6.6 to 6.9:

Sabatier Reaction:

CO₂+4H₂

CH₄+2H₂O ΔG ₂₉₈=−130,820 J/mol  (17.0)

TABLE 6.6 Free Energy for Sabatier versus Temperature Temperature (° C.)ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 25 −130,820 −253,016 −410.053 200−81,278 −173,571 −195.123 400 −40,645 −181,802 −209.743 600 2,192−187,985 −217.843

Methanol Synthesis Reaction via CO₂:

CO₂+3H₂

CH₃OH+H₂O ΔG ₂₉₈=−9,163 J/mol  (17.1)

TABLE 6.7 Free Energy for Methanol Reaction via CO₂ versus TemperatureTemperature (° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 25 −9,163 −131,010−408.882 200 37,223 −57,776 −200.844 400 78,725 −64,499 −212.814 600121,964 −69,135 −218.899

Bosch Reaction:

CO₂+2H₂

C+2H₂O ΔG ₂₉₈ ⁰=−80,001 J/mol  (17.2)

TABLE 6.8 Free Energy for Bosch Reaction versus Temperature Temperature(° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 25 −80,001 −178,148 −329.329 200−45,909 −93,505 −100.627 400 −25,129 −96,895 −106.636 600 −3,412 −99,659−110.249

Reverse Water Gas Reaction:

CO₂+H₂

CO+H₂O ΔG ₂₉₈=20,073 J/mol  (17.3)

TABLE 6.9 Free Energy Reverse Water Gas Reaction versus TemperatureTemperature (° C.) ΔG (kJ/mol) ΔH (J/mol) ΔS (J/mol) 25 20,073 −2,841−76.891 200 21,570 40,064 39.099 400 14,095 38,149 35.740 600 7,22936,068 33.035Thermodynamic data for the formation of methanol with CO and hydrogen isprovided in Table 6.9. Since this reaction is spontaneous at 25° C. thisreaction could be maintained as spontaneous at higher temperatures (forimproved kinetics) with an adjustment in the reactants partial pressures(an increase). The formation of methanol with CO and H₂ (reaction 17.4)is very effective since the hydrogen utilized is not wasted in theformation of water—therefore a reaction sequence for direct synthesis ofDME and other hydrocarbons.

Methanol Synthesis Reaction Via CO:

CO+2H₂

CH₃OH ΔG ₂₉₈ ⁰=−29,236 J/mol  (17.4)

TABLE 6.9 Free Energy for Methanol Reaction No. 2 versus TemperatureTemperature (° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 25 −29,236 −128,169−331.991 200 15,653 −97,839 −239.942 400 64,630 −102,647 −248.554 600114,735 −105,204 −251.934

The direct formation of DME can be performed through the reaction of CO₂with H₂ via reaction 17.4. The associated thermodynamics for thisreaction are provided in Table 6.10. DME can also be formed with CO andH₂ via reaction 17.5 without any waste of hydrogen due to the formationof water (this is therefore the preferred reaction). In Table 6.11 thethermodynamic data for reaction 17.4 is provided.

Dimethyl Ether Reaction Via CO₂:

2CO₂+6H₂

CH₃OCH₃+3H₂O ΔG ₂₉₈ ⁰=−97,598 J/mol  (17.5)

TABLE 6.10 Free Energy for Dimethyl Ether Reaction No. 1 versusTemperature Temperature (° C.) ΔG (kJ/mol) ΔH (J/mol) ΔS (J/mol) 25−97,598 −348,068 −840.501 200 1,745 −187,290 −399.651 400 83,737−197,714 −418.205 600 168,431 −204,919 −427.663

Dimethyl Ether Reaction Via CO:

2CO+3H₂

CH₃OCH₃+½O₂ ΔG ₂₉₈ ⁰=+99,470 J/mol  (17.6)

TABLE 6.11 Free Energy for Dimethyl Ether Reaction No. 2 versusTemperature Temperature (° C.) ΔG (J/mol) ΔH (J/mol) ΔS (J/mol) 2599,470 −56,552 −523.563 200 179,020 −23,845 −428.889 400 265,820 −28,602−437.476 600 353,582 −30,057 −439.449

The dissociation of water as in reaction 17.7 is associated withconsiderable energy costs due to the unfavourable thermodynamics (seeTable 6.12). This is the reason, as previously mentioned, to avoidhydrocarbon formation reactions which form water as a product orotherwise select reactions which minimize water formation.

Water Dissociation

H₂O

H₂+½O₂ ΔG ₂₉₈ ⁰=+237,200 J/mol  (17.7)

TABLE 6.12 Free Energy for Water Dissociation versus TemperatureTemperature (° C.) ΔG° (J/mol) 25 237,200 200 220,400 400 210,300 600199,600

III. Devices and Processes Using Ultrasound to Produce Hydrocarbons

Another embodiment of the invention is a device and method to producehydrocarbons from hydrogen and carbon sources wherein ultrasonic energyis applied to kinetically drive the reactions. All the foregoingdiscussed sources of carbon, such as carbon dioxide, and all foregoingsources of hydrogen, such as water, ammonia, and H₂S and all the variousways of obtaining those reactants, such as by plasma, electrolysis, andthe like, may be utilized in the ultrasonic reactions.

The present day generation of ultrasound was established with thediscovery of the piezoelectric effect by the Curies. Modern ultrasonicdevices rely on transducers (energy converters) which are composed ofpiezoelectric material. These materials respond to the application of anelectrical potential across opposite faces with a small change indimension. When the electrical potential is alternated at highfrequencies the crystal converts the electrical energy to mechanicalvibration (sound) energy. At sufficiently high alternating potential,high frequency sound (ultrasound) will be generated. When more powerfulultrasound at a lower frequency is applied to a system it is possible toproduce chemical changes as a result of acoustically generatedcavitation.

Ultrasound can be defined as sound with a frequency above that of normalhuman hearing (i.e. higher than 16 kHz). The frequency range involvinghigh energy—low frequency waves known as power ultrasound lies between20 and 100 kHz. This range is applied to cleaning, sonochemistry andplastic/metal welding. Very high frequencies are not required as theformation of bubbles requires a finite time (a 20 kHz rarefaction athalf cycle takes 25 μs—whereas a 20 MHz rarefaction only lasts 0.025μs). Frequencies from 1 MHz to 10 MHz are used for diagnostic andmedical applications.

Ultrasound provides a form of energy for the modification of chemicalreactivity which is different from heat, light, and/or pressure. Powerultrasound produces its effects via cavitation bubbles. These bubblesare created during the rarefaction cycle of the wave when the liquidstructure is torn apart to form tiny voids which collapse in thecompression cycle. Collapse of bubbles in liquids results in an enormousconcentration of energy due to the conversion of kinetic energy of theliquid motion into the heating of the bubble contents. It is possible tocreate pressures of hundreds of atmospheres and temperatures thousandsof degrees. These conditions induce chemical reactions yielding productsthat are typical of pyrolysis reactions in the gas phase.

There are three main classes of reaction mixture which can besignificantly affected through the application of an ultrasonic field,all which may be used in the present methods and devices.

-   -   Heterogeneous, solid-liquid systems such as those found in the        synthesis of many organometallic reagents containing magnesium,        lithium, zinc, etc. in which a solid metal reacts with organic        reagents dissolved in a suitable solvent.    -   Heterogeneous, liquid-liquid systems comprising two immiscible        liquids, for example water and styrene, in which the formation        of an emulsion and the increase in interfacial interaction are        important.    -   Homogeneous liquids such as water and alkanes or solutions. For        example sonification of carboxylic acid gives CO, CO₂ and        hydrocarbons.

In aqueous solutions, the thermal decomposition of water leads to theformation of highly reactive H. atoms and OH. radicals within thecavitation bubbles, but not in the bulk of the solution. There areactually three different regions of reactions occurring in cavitationconsisting of:

-   -   The interior of the collapsing gas bubbles in which extreme        conditions of temperature result in reactions typical of        pyrolysis.    -   The second region is the interfacial region between the        collapsing gas bubbles and the bulk solvent where the        temperatures are lower but still capable of inducing        free-radical reactions.    -   In the third region, that of the bulk solvent, the free radicals        escape into the bulk solution and undergo scavenging reactions        similar to those observed in aqueous radiation chemistry.

Heating and cooling rates are above 10¹⁰ K/sec a reaction quench ratewould ensure that the reaction products are stable. The extremely hightemperature local temperatures (measured at up to 20,000K) andpressures. In addition, sonofusion processes have been calculated toresult in pressures of 10 trillion kPa and 100 million ° C. which isabout 20,000 times that of the sun's surface.

With reactions of solids there are two types of reactions involvingmetals. Both are applicable in the present methods and devices. One iswhere the metal is a reagent and is consumed in the process. The secondis where the metal functions as a catalyst. It is assumed that anycleansing of the metal surfaces enhances their chemical reactivity. Inaddition, sonification efficiently removes reactive intermediates, orproducts, cleaning the metal surface and therefore providing clean metalsurfaces for reaction. Sonification also provides the possibility ofenhanced single electron transfer (SET) reactions at the metal surface.

Heterogeneous Reactions—Involving Powders or Other Particulate Matter

The processes and devices wherein ultrasonic energy is applied may usean optional catalyst. Catalytic reactions frequently use heterogeneouscatalysts consisting of rare and expensive metals. The use of ultrasoundprovides the opportunity of activating less reactive and also lessexpensive metals. The application of ultrasound to heterogeneouscatalysis consists of the following areas: (1) in the formation ofsupported catalysts; (2) in the activation of preformed catalysts; and(3) the enhancement of catalytic behavior during a catalytic reaction.

The efficiency of heterogeneous reactions involving solids dispersed inliquids will depend upon the available reactive surface area and masstransfer. Conventional technology utilizes agitating and stirring withrotating devices and baffled pipes when mixing, reacting or dissolvingsmall and submicron sized particles on an industrial scale. Withconventional rotational mixing techniques, dispersing solid particles 10microns in diameter or smaller in a liquid reaches a barrier determinedby the rate of mixing and transfer within a liquid. This limit calledthe mass transfer coefficient, K, reaches a constant value of about0.015 cm/sec in water, and cannot be increased any further. This holdstrue for liquids of similar viscosity. Sonification or power ultrasoundovercomes this limitation and greatly enhances mixing. For example, masstransport of substrate molecules to an electrode surface from bulksolution is accelerated via a cavitational micro-jet stream with avelocity in excess of 100 m s⁻¹.

The shock wave resulting from cavitation collapse results in intensivecleaning of metal surfaces, the removal of passivating coatings existingon metal surfaces (e.g. oxides, carbonates and hydroxides) and thepitting of metal surfaces—which increases the possible reaction area.For example, it is possible to prepare amorphous nanopowders viadecomposition of organometallic compounds, such as the synthesis ofFe/SiO₂ catalyst. This catalysts material may be used for activity andselectivity for CO hydrogenation to hydrocarbons (Fischer-Tropschprocess) in the range between 200 to 300° C. and at 1 atm pressure.Sonochemically produced iron on silica catalyst is an order of magnitudemore active than conventional supported iron at similar loadings anddispersions. In addition, this silica supported nanostructured ironcatalyst exhibits high activity at low temperatures (<250° C.) whereasconventional silica supported iron catalyst has no activity. The majorreaction products for both nanostructured and conventional catalysts areshort-chain C₁ to C₄ hydrocarbons at temperatures above 275° C. (above275° C. recrystallization of the catalyst can occur). At temperaturesbelow 275° C. the nanostructured catalyst has higher selectivity towardslog-chain hydrocarbons (C₅₊).

Homogeneous Reactions

There are a variety of homogeneous reactions that may be employed, forexample, the emission of light from water (sonoluminescence), thefragmentation of liquid alkanes, the liberation of iodine from aqueouspotassium iodide, or the acceleration of homogeneous solvolysisreactions. These reactions occur at an accelerated rate not due to themechanical effects of sonification alone. The acceleration ofhomogeneous reactions is due to the process of cavitational collapse.Inside the microbubble exists vapor from the solvent and any volatilereagents that are subjected to enormous increases in pressure andtemperature. Under these conditions the solvent and/or reagent undergoesfragmentation to generate reactive species of the radical or carbinetype enough to fluoresce in some situations. In addition, the shock waveproduced by bubble collapse could also disrupt the solvent structure andalter the reactivity by altering salvation of the reactive speciespresent.

Several benefits of using ultrasonic energy are: (1) reactions can beaccelerated or less severe conditions can be required if sonification isutilized; (2) sonochemical reactions can use cruder reagents thanconventional techniques; (3) induction times are usually significantlyreduced as are exotherms associated with such reactions; (4) reactionsare often initiated by ultrasound without the need for additives; (5)the number of steps that are normally required in a synthetic route canbe reduced; and (6) in some cases a reaction can be directed to analternative pathway.

There are several factors that can be controlled for cavitation. Theseinclude:

Frequency—as the ultrasonic frequency is increased the production andintensity of cavitation in liquids decreases. However, higherfrequencies are advantageous when radical promotion is required.

Solvent—Cavitation is more difficult to produce in viscous liquids orliquids with high surface tensions

Temperature—Increasing the reaction temperature allows cavitation to beachieved at lower acoustic intensity. Unfortunately, the effectsresulting from cavitational collapse are also reduced. Therefore, to getmaximum sonochemical benefit the reaction should be conducted at as lowa temperature as possible or with a solvent of low vapor pressure.

Gas type and content—Employing gases with large values of the heatcapacity ratio, γ (γ=C_(p)/C_(v)) provide larger sonochemical effectsfrom gas filled bubbles. Therefore monoatomic gases such as He, Ar andNe are used in preference to diatomics such as N₂, air, O₂, etc. Itshould also be noted that sonochemical effects also depend upon thethermal conductivity of the gas. The greater the thermal conductivity ofthe gas the more heat will be dissipated to the surrounding liquid,effectively decreasing the maximum temperature, T_(Max). In addition,utilizing gases with increased solubility will reduce the thresholdintensity and the intensity of cavitation.

External Applied Pressure—Increasing the external pressure leads to anincrease in both the cavitational threshold and the intensity of thebubble collapse. Increasing the pressure will result in more rapid andviolent bubble collapse.

Intensity—An increase in intensity in the ultrasound will result in anincrease in the sonochemical effects. Cavitation bubbles, which aredifficult to create at higher frequencies are now possible. The bubblecollapse will also be more violent.

Vapor Pressure—The vapor pressure of the solvent cannot be too high asin the case of organic materials at room temperature (they will notcavitate under these conditions). However if the temperature of thesolvent is kept well below its boiling point (so that the vapor pressureis kept low) then all organic liquids will undergo sonochemistry voahomolysis of bonds and with the formation of free radicals.

Sonoelectrochemistry is considered to be the interaction of sound withelectrochemistry which is the interconversion of electrical and chemicalenergies. This would include important industrial processes such aselectrodeposition (electroplating), electro-organic synthesis andgeneration of power in liquid fuel cells. The application of ultrasoundto these devices enhances their performance due to the followingfactors:

-   -   The application of ultrasound decreases the thickness of the        diffusion layer next to the electrode and in doing so assists        the electrode reactions. Conventional stirring or mixing reduces        the thickness of this layer; however, ultrasonic stirring is by        far the most effective method.    -   Ultrasound increases the movement of metal ions which reduces        the concentration effect. Where there is dissolution of the        anode the concentration of metal ions increases at high current        densities—the rate of dissolution is greater than the rate of        diffusion away from the metal surface into the bulk solution.        The electrolytic process thereby slows down—with ultrasound the        diffusion rate would increase resulting in an increase in        performance.    -   When a gas molecule to be discharged energy is required to        dislodge it from the electrode surface—this is called the        activation polarization. An example of ultrasonically assisted        gas evolution is with the evolution of chlorine from carbon        electrodes which was found to be significantly improved with        ultrasound (i.e. decreased activation polarization).    -   A significant reduction in electrode fouling, a problem        encountered in electro-organic synthesis. Ultrasonics        continuously clean the surface of an electrode.    -   Using ultrasound minimizes the difference in concentration        around the electrodes increasing the performance of        electro-catlytic reactions. Kinetic limitations due to mass        transport in a reaction are reduced by orders of magnitude with        ultrasonic activation.    -   There is a reduction in resistance polarization for a liquid        electrolyte which contributes to ohmic drop in an        electrochemical cell. The electrochemical cell experiences less        power loss due to resistance polarization.

The application of ultrasound to an electrolytic solution is beneficialin that it reduces the ohmic, activation and concentrationover-potentials thereby enhancing the performance of electrochemicaldevices.

In summary the use of ultrasound in electrochemistry includes:

Degassing of the electrode surface—reduction in activation polarization

Disruption of the diffusion layer which reduces depletion ofelectroactive species—reduction in mass transport of concentrationlosses

Improved mass transport of ions across the diffusion layer

Continuous cleaning and activation of the electrode surfaces—reductionin activation polarization

Sono-Electro-Organic Synthesis

Ultrasound provides benefits in electro-organic synthesis due itsability to clean surfaces, form fresh surfaces and improve masstransport (which could involve kinetic and thermodynamic requirements).At benefit with ultrasound is that there will be no electrode foulingfor organic synthesis and that reactions maintain a consistent currentdensity at a steady and lower voltage. One explanation is that enhancedmass transport under ultrasound and the abrasion effect near theelectrode surface sweeps the inhibiting species into solution and indoing so keeps the electrode surface clean. There is also typically alowering in the applied cell voltage required, representing an energysaving. In summary sono-electro-organic synthesis can produce alteredproduct ratios, greater efficiencies, lessened cell power requirementsand a diminution of electrode fouling. Ultrasound can also influencemultiphase systems and is therefore useful for reactions involvingimmiscible materials.

When ultrasonic irradiation is powerful enough to induce cavitation itis possible to introduce a range of additional energy sources which canbehave in a synergistic manner. These additional sources can bemechanical agitation, ultraviolet light, other ultrasonic frequencies,electrochemistry, infrared, magnetic fields and microwaves. For exampleunder normal ultrasonic irradiation sonoluminescence (SL) occurs duringthe compression phase of the bubble, whereas when exposed to microwaves,SL occurs during both contraction and expansion of the bubble. Theefficiency of a sonochemical reaction is significantly increased bysimultaneous irradiation with microwaves and it would be possible toachieve new chemical effects.

When sonification is added acoustic cavitation and shock waves generatean intense mixing which leads to a vessel that is a perfectly agitatedreactor. This implies that the concentration of the solutes is the sameat any point within the vessel. Therefore, if the concentration of theexcited species becomes independent of distance, the reaction ratesshould be the same at any point in the solution. No local depletion ofintermediates would result with a preferred result on bimolecularreactions.

In order to improve the overall performance of a photoprocess,heterogeneous photocatalysis has been combined with physical or chemicaloperations, which affect the chemical kinetics and or overallefficiency. This combination can: (1) increase the efficiency anddecrease the reaction time with respect to separated operations; or (2)decrease the cost with respect to heterogeneous photocatalysis alone,generally in terms of light energy.

Heterogeneous photocatalysis is coupled with an operation that affectsthe photocatalytic mechanisms therefore improving the efficiency of thephotocatalytic process. The coupling can be with: (1) ultrasonicirradiation; (2) Photo-Fenton reaction; (3) Ozonation; and (4)Electrochemical treatment.

Another embodiment employs the combination of ultrasound andphotocatalysis (sonophotocatalysis). The simultaneous use of bothtechniques is capable of degrading organic pollutants in water which isnot normally possible. Ultrasound and photocatalysis has been combinedfor the degradation of various organics such as salicyclic acid,propyzamide, oxalic acid, 2,4,6-trichlorophenol, and chlorinatedaromatic compounds. It is possible to decompose water to H₂ and O₂through the use of sonophotocatalysis where TiO₂ is utilized as thephotocatalyst. The combination of sonolysis and photocatalysis permitsthe decomposition of water.

To initiate the growth of a cavitation bubble, an acoustic pressureabove the so called Blake threshold pressure has to be applied. TheBlake threshold is the acoustic pressure amplitude necessary to cause abubble initially in a state of stable equilibrium, to lose its stabilityand grow, rapidly increasing its volume. This loss of mechanicalstability and rapid growth is essential to cavitation nucleation andtransient cavitation processes. The Blake threshold pressure (which is anegative pressure) is associated with the destruction of microbubblesand is approximated according to the following equation:

$\begin{matrix}{P_{B} = {P_{h} + {\frac{8\sigma}{9}\left( \frac{3\sigma}{2\; P_{h}R_{e}^{3}} \right)^{1/2}}}} & (18.0)\end{matrix}$

where P_(B) is the Blake threshold pressure, P_(h) is the hydrostaticpressure, σ is the surface tension, R_(e) is the radius of a bubble atequilibrium (neither contracting or expanding).

The critical Blake radius for rapid expansion of a bubble can also beapproximated by:

R _(c)≈2R _(e)  (18.1)

where R_(c) is the critical Blake radius and R_(e) is the equilibriumradius of the microbubble.

As expected according equation 18.0, due to the increase in hydrostaticpressure (P_(h)) during pressurization of a liquid, the Blake thresholdincreases, which implies that higher negative acoustic pressures areneeded to produce cavitations.

In ordinary solvents, cavitation does not occur at elevated pressurestherefore sonochemical studies have been limited to atmosphericpressures. Unlike ordinary liquids/solvents, the high vapor pressure ofa dense phase fluid such as CO₂ (which is a gas at ambient conditions)allows cavitation to occur. The occurrence of cavitation in highpressure CO₂ has been shown at 75 bar and 283K where CO₂ is in a liquidstate, even though it is above its critical pressure. Staying below thecritical point of the mixture may be desirable, since above the criticalpoint of the mixture no phase boundaries exist, which would prohibitcavitation. At an acoustic intensity below the Blake threshold pressure(25 W/cm²) the CO₂ fluid at 75 bar remains transparent, while at 125W/cm² cavitation occurs. The Blake threshold pressure was calculated as:

$\begin{matrix}{P_{B} = {P_{h} - P_{v} + {\frac{4}{3}\sigma \sqrt{\left( \frac{2\sigma}{3\; {R_{e}^{3}\left( {P_{h} + \frac{2\sigma}{R_{e}} - P_{v}} \right)}} \right)}}}} & (18.2)\end{matrix}$

where P_(v) is the vapor pressure of the fluid (this term is absent inequation 18.0).

No bubble formation occurs in water at elevated pressures—the maximumbubble radius before collapse is on the same order of magnitude forwater at ambient pressure and with CO₂ at high pressure. The calculatedmaximum attainable temperatures are 722K for water (at 1 bar) and 585Kfor liquid CO₂ at 58.2 bar.

Gas-to-liquid processes of Fischer-Tropsch synthesis, methanolsynthesis, dimethyl ether (DME) synthesis, and synthesis of syntheticgasoline have received attention from industrial and academic sectors.One of the present inventions is to expand the products of gas-to-liquidprocesses to a wide range of additional chemical products. Theseproducts include dimethyl ether (DME), olefins via themethanol-to-olefin (MTO) process, synthetic gasoline via the methanol togasoline (MTG) process or the olefin-to-gasoline and distillate process(MOGD) process. These compounds are synthesized in the presence ofzeolite catalysts, commercially described as ZSM-x type catalysts. Inthe MOGD reaction, ZSM-5 oligomerizes light olefins from either refinerystreams or the MTO process into gasoline, distillate and lubricant. Inan analogous fashion to Fischer Tropsch synthesis, the processing ofliquid CO₂ will result in a wide range of hydrocarbon products.

The main components in the sonochemical synthesis of hydrocarbonsconsist of CO₂—CO, H₂O—H₂ and an appropriate catalyst depending on whatproducts are required. Sonochemistry consists of all of the chemicaleffects that are induced by ultrasound, including the formation ofradicals and the enhancement of reaction rates at ambient temperatures.The chemical effects of ultrasound are caused by cavitation whichinvolves the collapse of microscopic bubbles in a liquid. Duringcollapse of the bubbles temperatures of up to 5000K and pressures of 200atmosphere and higher are created. These extreme conditions results inthe formation of excited states, bond breakage and the generation ofradicals. Cavitation induced radical reactions provide clean and safeoperations, because no separation is required afterwards and theformation of radicals can be controlled externally.

Carbon dioxide is non-flammable, a significant safety advantage in usingit as a solvent. It is naturally abundant with a threshold limit value(TLV) of 5,000 ppm at 298K and unlimited exposure to workers. Clearlycarbon dioxide is a greenhouse gas but it is also a naturally occurringabundant material. The objective of one method of this invention is towithdraw CO₂ from the environment, employ it in a process and thenreturn it to the environment with no overall environmental effect. Intheory, CO₂ can be extracted from the atmosphere or from the stack of acarbon based combustion source. Most of the CO₂ is derived from eitherNH₃ plants or from tertiary oil recovery. Through proper management ofCO₂ instead of being a pollutant it will become a valuable molecule. Incombination with the global water cycle the global carbon dioxide cyclewould be managed responsibly in a sustainable manner.

In one method of the invention, liquid carbon dioxide may be used as amedium for ultrasound induced chemical reactions—with high molecularweight polymers being prepared in high-pressure fluid. In ordinarysolvents, the process of bubble formation and implosion (i.e.cavitation) does not occur at elevated pressure. However, the high vaporpressure of dense fluids such as CO₂ counteracts the hydrostaticpressure, permitting cavitation to occur. It is possible in thisapplication to initiate chemical reactions with or without using organicsolvents and/or initiators/catalysts via ultrasonics.

Sonochemical reduction of carbon dioxide dissolved in water may resultin various products such as CO, H₂O₂, H₂ and O₂. Carbon dioxidedissolved in water may be reduced sonochemically to CO. In addition, H₂and a small amount O₂ may be formed. A series of pure gases were passedthrough the water to displace dissolved air. It was determined that thereduction rate for CO₂ according to the pure gas utilized followed theorder Ar>He>H₂>N₂. In addition, it was determined that the efficiency ofCO₂ reduction decreased with increasing temperature—with 5° C. beingoptimal. Regardless, several factors determine the rate ofsonolysis/reduction consisting of; surface tension, viscosity, soundvelocity, etc. The reduction of CO₂ was performed by adding CO₂ to anArgon atmosphere the gas mixture which subsequently dissolves in water.It was determined that the maximum reduction rate of CO₂ was obtainedwhen the gas concentration reached 0.03 mole fraction of CO₂ above thewater's surface. Carbon monoxide and hydrogen were determined to be themain products from sonolysis of Ar—CO₂ mixtures dissolved in water.

Upon formation of compounds the viscosity of the solution can change. Ahigh viscosity fluid hinders cavitation and reduces the production rateof radicals. The fluid to be utilized should act as an anti-solvent forthe chemical being produced. For example, high pressure CO₂ readilydissolves most monomers whereas it exhibits low solubility with polymersand therefore acts as an anti-solvent and results in precipitation ofpolymers. Cavitation is possible if the difference between the staticand vapor pressure is smaller than the maximum acoustic pressure thatcan be applied. In the case of liquid carbon dioxide its high vaporpressure is capable of counteracting a high static pressure.

According to calorimetric studies a substantial amount of acousticenergy is not converted into the formation of radicals. Typically, theenergy yield for the formation of radicals is in the order of 5×10⁻⁶J/J. Only in the immediate vicinity of the ultrasonic tip doescavitation occur, this being the location where free radicals areproduced. It follows that the area directly adjacent to the ultrasonicemitter is where the reactions will occur primarily. Therefore, it wouldbe advantageous to locate any required catalysts or electrodesimmediately adjacent to the ultrasonic emitter.

The number of radicals formed due to sonification is a function of thenumber of cavities created and the number of radicals formed percavitation bubble. The extrinsic parameters, including, pressure,temperature, ultrasound settings and the type of fluid, effect theformation of radicals in a complex way. Temperature has a significanteffect on the formation of radicals, especially at low temperatures. Dueto the cushioning effect of increased vapor pressure at highertemperatures during the implosion of the cavity, the local temperaturesgenerated inside the cavity are lower at higher overall temperatures.Regardless, the energy efficiency decreases at higher temperatures dueto lower radical formation rates.

It is inefficient to use high ultrasonic amplitudes, therefore a largersonofication area is more efficient. Increasing the coupling of theacoustic energy from the emitter. For example, a large cloud ofcavitation bubbles is formed close to the emitter for intense soundfields, which absorbs and scatters the sound wave. Reduction orelimination of this bubble cloud would increase the ultrasonic couplingefficiency.

Supercritical CO₂ will exhibit a higher compressibility than liquid CO₂and therefore supercritical fluid may be better able to absorb excessheat evolved from an exothermic reaction that has run away from normaloperating conditions. This is especially important with the highlyexothermic reactions present in formation of hydrocarbons via FischerTropsch processes. There is evidence for the application of ultrasonicsto supercritical fluids with improvements noted in extraction processes.Ultrasonic cavitation has been analyzed and determined to be favored bylower temperature and higher pressure with supercritical CO₂.

With the dramatic increase in the international oil price, gas-to-liquidprocesses, including Fischer-Tropsch synthesis, methanol synthesis anddimethyl ether synthesis are becoming increasingly important. The slurryreactor has advantages of simpler construction, good heat transfer andfeasible scale-up. Therefore, a slurry reactor may be used in additionto a fixed bed reactor in the gas-to-liquid processes. In a slurryreactor, fine catalyst particles are suspended in an oil solvent whichpossesses a large heat capacity. The bubbles agitate the oil solvent,and since the oil solvent has a high heat transfer rate, temperaturesare maintained uniformly. This is especially important due to the highlyexothermic nature of methanol synthesis, DME synthesis and synthesis ofa wide range of hydrocarbons. In one aspect of the invention, theapplication of ultrasonics to slurry type processes provides severaladvantages: mixing would be complete, mass transport limitations wouldbe eliminated, the surface of catalysts/electrocatalysts would becleaned continuously, reaction temperatures and pressures inside thecavitation bubbles could be tailored for the desired hydrocarbonspecies, and the bulk solution could be at ambient temperature andpressures.

In slurry or any other process which contains catalyst/electrocatalystsuspended in solution the separation and recovery of this material isimportant. There are several ways in which catalysts can be recoveredafter a reaction has proceeded and then reused. Depending on the formthe catalysts are in, recovery may consist of: (1) through lowering ofthe reaction pressures so as to precipitate the catalyst from thereaction fluids; (2) by cooling of the fluid until the catalystsprecipitates; (3) by using a membrane in which the reaction products topass through but not the catalyst; (4) through auto-separation of aproduct which is insoluble in the reaction fluid; (5) by dissolution ofthe catalyst in a liquid that is immiscible with the reaction/productfluids; (6) by attaching the catalyst to a solid polymer or other solidsupport; (7) by using an inverted biphasic system in which the catalystpartitions into a liquid that is immiscible with the reaction fluid; and(8) separation of catalysts fines using a high gradient magneticseparation device.

Several of the ultrasonic or sonochemical processes described herein maybe used in combination with several electrolytic, electrochemical, andplasma processes described above. For example, the carbon reactant forthe ultrasonic or sonochemical process may be obtained through any ofthe processes detailed above, including, but not limited to plasma andthe carbon dioxide extraction unit. For example, the hydrogen reactantfor the ultrasonic or sonochemical process may be obtained through anyof the processes detailed above, including, but not limited to, plasmaand electrolysis.

FIG. 13 illustrates an ultrasonic process and device according to theinvention. The hydrogen source 1310 enters the reactor 1340. Thehydrogen source 1310 optionally passes through an electrolytic membrane1320 entering the reactor 1340. The reactor preferably contains catalyst1330. Inside the reactor, preferably is liquid carbon dioxide dissolvedin water and other solvents. Carbon dioxide 1360 may also be supplied ingaseous form. An ultrasonic transducer 1350 supplies energy to drive thereaction. Exiting the reactor 1370 are the produced hydrocarbons.

FIG. 14 illustrates a device 1450 to produce hydrogen gas from ahydrogen source using an ultrasonic electrocatalytic electrode. Ahydrogen source 1410 enters the device 1450. One or more ultrasonictransducers 1430 supply energy to drive the reaction. Inside the deviceare anode and cathode, and an optional catalyst. The ultrasonictransducers 1430 create the potential across the electrodes. Beforeexiting, the hydrogen gas (1460) passes through an electrolyticmembrane.

The source of hydrogen is preferably hydrogen gas. It may enter thereactor after a pretreatment step. The source of carbon is preferablyliquid carbon dioxide gas, which may be placed under about 5 atmospheresof pressure at roughly room temperature. Inside the reactor, a catalystmay be used. The temperature and pressure within the reactor ispreferably about less than 150° C. and less than about 3 atmosphere. Theenergy supplied to the reactor is preferably generated from a renewableenergy source that is converted into ultrasonic energy prior to beingapplied to the reactor on the order of about greater than 10 kHz. Thereactor may be a small sized reactor such that it fits within acombustion engine. The reactor may also be scaled to industrial size.Preferably, it is a slurry based reaction with catalyst. The resultinghydrocarbon is preferably methanol or ethanol.

Similar to the electrolytic reaction described in Section I, theultrasonic energy may be derived from an electrical energy source thatis generated from a renewable energy source, such as winder and/orsolar.

Any of the hydrocarbons produced by the methods and devices describedherein may be used for alternative energy fuels or any other suitablepurpose, such as feedstock for the production of plastics.

The foregoing detailed description is provided solely to describe theinvention in detail, and is not intended to limit the invention. Thoseskilled in the art will appreciate that various modifications may bemade to the invention without departing significantly from the spiritand scope thereof.

1. A device for the gas-phase electrochemical reduction of acarbon-containing gas to produce one or more hydrocarbons, comprising: acarbon dioxide-containing gas input; a first cathode in fluidiccommunication with the carbon dioxide-containing gas input connected toa first anode through an anionic-conducting electrolyte; a secondcathode in fluidic communication with the first cathode and at apressure between about 1 atm to about 15 atm and a temperature betweenabout 100° C. to less than about 900° C. and connected to a second anodethrough a protonic-conducting electrolyte; a hydrogen-source input influidic communication with the second anode; a source of electricalpotential electrically connected to the first cathode and the firstanode; and a source of electrical potential electrically connected tothe second cathode and the second anode.
 2. The device of claim 1,further comprising a plasma energy-source.
 3. The device of claim 2,wherein the plasma energy-source is in communication with the secondcathode.
 4. The device of claim 2, wherein the plasma energy-source isin communication with the second anode.
 5. The device of claim 1,further comprising an ultrasonic energy-source.
 6. The device of claim5, wherein the ultrasonic energy-source is in communication with thesecond cathode.
 7. The device of claim 5, wherein the ultrasonicenergy-source is in communication with the second anode.
 8. The deviceof claim 1, wherein the first cathode is selected from the groupconsisting of metal electrocatalysts, metal-supported electrocatalysts,metal-oxide supported electrocatalysts, electrocatalytic superconductingmaterials, and combinations thereof.
 9. The device of claim 1, whereinthe first anode is selected from the group consisting ofplatinum-ruthenium electrocatalysts, platinum-iridium electrocatalysts,IrO₂ electrocatalysts, ultrafine IrO₂ powder combined with platinumelectrocatalysts, and combinations thereof.
 10. The device of claim 1,wherein the protonic-conducting electrolyte is selected from the groupconsisting of polymeric protonic conductors, solid acid protonicconductors, ceramic mixed oxide protonic conductors, and combinationsthereof.
 11. An electrochemical system for the gas-phase reduction of acarbon-containing gas to produce one or more hydrocarbons, comprising: acarbon dioxide-containing gas; a first input for receiving the carbondioxide-containing gas; a first cathode in fluidic communication withthe first input connected to a first anode through an anionic-conductingelectrolyte; a second cathode in fluidic communication with the firstcathode and at a pressure between about 1 atm to about 15 atm and atemperature between about 100° C. to less than about 900° C. andconnected to a second anode through a protonic-conducting electrolyte; ahydrogen-source; a second input for receiving the hydrogen-source and influidic communication with the second anode; a source of electricalpotential electrically connected to the first cathode and the firstanode; and a source of electrical potential electrically connected tothe second cathode and the second anode.
 12. The electrochemical systemof claim 11, further comprising a plasma energy-source.
 13. Theelectrochemical system of claim 12, wherein the plasma energy-source isin communication with the second cathode.
 14. The electrochemical systemof claim 12, wherein the plasma energy-source is in communication withthe second anode.
 15. The electrochemical system of claim 11, furthercomprising an ultrasonic energy-source.
 16. The electrochemical systemof claim 15, wherein the ultrasonic energy-source is in communicationwith the second cathode.
 17. The electrochemical system of claim 15,wherein the ultrasonic energy-source is in communication with the secondanode.
 18. The electrochemical system of claim 11, wherein the firstcathode is selected from the group consisting of metal electrocatalysts,metal-supported electrocatalysts, metal-oxide supportedelectrocatalysts, electrocatalytic superconducting materials, andcombinations thereof.
 19. The electrochemical system of claim 11,wherein the first anode is selected from the group consisting ofplatinum-ruthenium electrocatalysts, platinum-iridium electrocatalysts,IrO2 electrocatalysts, ultrafine IrO2 powder combined with platinumelectrocatalysts, and combinations thereof.
 20. The electrochemicalsystem of claim 11, wherein the protonic-conducting electrolyte isselected from the group consisting of polymeric protonic conductors,solid acid protonic conductors, ceramic mixed oxide protonic conductors,and combinations thereof.